diff --git a/beacon-chain/blockchain/process_attestation_helpers.go b/beacon-chain/blockchain/process_attestation_helpers.go
index 8dbeed9aa5..b6e5227d5d 100644
--- a/beacon-chain/blockchain/process_attestation_helpers.go
+++ b/beacon-chain/blockchain/process_attestation_helpers.go
@@ -32,14 +32,18 @@ func (s *Service) getAttPreState(ctx context.Context, c *ethpb.Checkpoint) (*sta
 
 	baseState, err := s.stateGen.StateByRoot(ctx, bytesutil.ToBytes32(c.Root))
 	if err != nil {
-		return nil, errors.Wrapf(err, "could not get pre state for slot %d", helpers.StartSlot(c.Epoch))
+		return nil, errors.Wrapf(err, "could not get pre state for epoch %d", c.Epoch)
 	}
 
-	if helpers.StartSlot(c.Epoch) > baseState.Slot() {
+	epochStartSlot, err := helpers.StartSlot(c.Epoch)
+	if err != nil {
+		return nil, err
+	}
+	if epochStartSlot > baseState.Slot() {
 		baseState = baseState.Copy()
-		baseState, err = state.ProcessSlots(ctx, baseState, helpers.StartSlot(c.Epoch))
+		baseState, err = state.ProcessSlots(ctx, baseState, epochStartSlot)
 		if err != nil {
-			return nil, errors.Wrapf(err, "could not process slots up to %d", helpers.StartSlot(c.Epoch))
+			return nil, errors.Wrapf(err, "could not process slots up to epoch %d", c.Epoch)
 		}
 		if err := s.checkpointState.AddCheckpointState(c, baseState); err != nil {
 			return nil, errors.Wrap(err, "could not saved checkpoint state to cache")
@@ -76,13 +80,17 @@ func (s *Service) getAttCheckPtInfo(ctx context.Context, c *ethpb.Checkpoint, e
 	// Retrieve checkpoint state to compute checkpoint info.
 	baseState, err := s.stateGen.StateByRoot(ctx, bytesutil.ToBytes32(c.Root))
 	if err != nil {
-		return nil, errors.Wrapf(err, "could not get pre state for slot %d", helpers.StartSlot(c.Epoch))
+		return nil, errors.Wrapf(err, "could not get pre state for epoch %d", c.Epoch)
 	}
-	if helpers.StartSlot(c.Epoch) > baseState.Slot() {
+	epochStartSlot, err := helpers.StartSlot(c.Epoch)
+	if err != nil {
+		return nil, err
+	}
+	if epochStartSlot > baseState.Slot() {
 		baseState = baseState.Copy()
-		baseState, err = state.ProcessSlots(ctx, baseState, helpers.StartSlot(c.Epoch))
+		baseState, err = state.ProcessSlots(ctx, baseState, epochStartSlot)
 		if err != nil {
-			return nil, errors.Wrapf(err, "could not process slots up to %d", helpers.StartSlot(c.Epoch))
+			return nil, errors.Wrapf(err, "could not process slots up to epoch %d", c.Epoch)
 		}
 	}
 	f := baseState.Fork()
@@ -155,7 +163,10 @@ func (s *Service) verifyBeaconBlock(ctx context.Context, data *ethpb.Attestation
 
 // verifyLMDFFGConsistent verifies LMD GHOST and FFG votes are consistent with each other.
 func (s *Service) verifyLMDFFGConsistent(ctx context.Context, ffgEpoch uint64, ffgRoot []byte, lmdRoot []byte) error {
-	ffgSlot := helpers.StartSlot(ffgEpoch)
+	ffgSlot, err := helpers.StartSlot(ffgEpoch)
+	if err != nil {
+		return err
+	}
 	r, err := s.ancestor(ctx, lmdRoot, ffgSlot)
 	if err != nil {
 		return err
diff --git a/beacon-chain/blockchain/process_attestation_test.go b/beacon-chain/blockchain/process_attestation_test.go
index 64cbcbc7bd..350833ddfc 100644
--- a/beacon-chain/blockchain/process_attestation_test.go
+++ b/beacon-chain/blockchain/process_attestation_test.go
@@ -90,7 +90,7 @@ func TestStore_OnAttestation(t *testing.T) {
 			name:          "no pre state for attestations's target block",
 			a:             &ethpb.Attestation{Data: &ethpb.AttestationData{Target: &ethpb.Checkpoint{Root: BlkWithOutStateRoot[:]}}},
 			wantErr:       true,
-			wantErrString: "could not get pre state for slot 0",
+			wantErrString: "could not get pre state for epoch 0",
 		},
 		{
 			name: "process attestation doesn't match current epoch",
@@ -212,7 +212,7 @@ func TestStore_OnAttestationUsingCheckptCache(t *testing.T) {
 			name:          "no pre state for attestations's target block",
 			a:             &ethpb.Attestation{Data: &ethpb.AttestationData{Target: &ethpb.Checkpoint{Root: BlkWithOutStateRoot[:]}}},
 			wantErr:       true,
-			wantErrString: "could not get pre state for slot 0",
+			wantErrString: "could not get pre state for epoch 0",
 		},
 		{
 			name: "process attestation doesn't match current epoch",
@@ -363,7 +363,9 @@ func TestStore_UpdateCheckpointState(t *testing.T) {
 	require.NoError(t, service.beaconDB.SaveState(ctx, baseState, bytesutil.ToBytes32(newCheckpoint.Root)))
 	returned, err = service.getAttPreState(ctx, newCheckpoint)
 	require.NoError(t, err)
-	baseState, err = state.ProcessSlots(ctx, baseState, helpers.StartSlot(newCheckpoint.Epoch))
+	s, err := helpers.StartSlot(newCheckpoint.Epoch)
+	require.NoError(t, err)
+	baseState, err = state.ProcessSlots(ctx, baseState, s)
 	require.NoError(t, err)
 	assert.Equal(t, returned.Slot(), baseState.Slot(), "Incorrectly returned base state")
 
diff --git a/beacon-chain/blockchain/process_block.go b/beacon-chain/blockchain/process_block.go
index 03150ea66c..d9cdd6d898 100644
--- a/beacon-chain/blockchain/process_block.go
+++ b/beacon-chain/blockchain/process_block.go
@@ -316,8 +316,11 @@ func (s *Service) handleBlockAfterBatchVerify(ctx context.Context, signed *ethpb
 func (s *Service) handleEpochBoundary(postState *stateTrie.BeaconState) error {
 	if postState.Slot() >= s.nextEpochBoundarySlot {
 		reportEpochMetrics(postState)
-		s.nextEpochBoundarySlot = helpers.StartSlot(helpers.NextEpoch(postState))
-
+		var err error
+		s.nextEpochBoundarySlot, err = helpers.StartSlot(helpers.NextEpoch(postState))
+		if err != nil {
+			return err
+		}
 		// Update committees cache at epoch boundary slot.
 		if err := helpers.UpdateCommitteeCache(postState, helpers.CurrentEpoch(postState)); err != nil {
 			return err
diff --git a/beacon-chain/blockchain/process_block_helpers.go b/beacon-chain/blockchain/process_block_helpers.go
index bba2911232..423fe5b4da 100644
--- a/beacon-chain/blockchain/process_block_helpers.go
+++ b/beacon-chain/blockchain/process_block_helpers.go
@@ -119,7 +119,10 @@ func (s *Service) VerifyBlkDescendant(ctx context.Context, root [32]byte) error
 // verifyBlkFinalizedSlot validates input block is not less than or equal
 // to current finalized slot.
 func (s *Service) verifyBlkFinalizedSlot(b *ethpb.BeaconBlock) error {
-	finalizedSlot := helpers.StartSlot(s.finalizedCheckpt.Epoch)
+	finalizedSlot, err := helpers.StartSlot(s.finalizedCheckpt.Epoch)
+	if err != nil {
+		return err
+	}
 	if finalizedSlot >= b.Slot {
 		return fmt.Errorf("block is equal or earlier than finalized block, slot %d < slot %d", b.Slot, finalizedSlot)
 	}
@@ -150,7 +153,11 @@ func (s *Service) shouldUpdateCurrentJustified(ctx context.Context, newJustified
 	}
 
 	newJustifiedBlock := newJustifiedBlockSigned.Block
-	if newJustifiedBlock.Slot <= helpers.StartSlot(s.justifiedCheckpt.Epoch) {
+	jSlot, err := helpers.StartSlot(s.justifiedCheckpt.Epoch)
+	if err != nil {
+		return false, err
+	}
+	if newJustifiedBlock.Slot <= jSlot {
 		return false, nil
 	}
 	var justifiedBlockSigned *ethpb.SignedBeaconBlock
@@ -310,7 +317,10 @@ func (s *Service) finalizedImpliesNewJustified(ctx context.Context, state *state
 		}
 
 		// Update justified if store justified is not in chain with finalized check point.
-		finalizedSlot := helpers.StartSlot(s.finalizedCheckpt.Epoch)
+		finalizedSlot, err := helpers.StartSlot(s.finalizedCheckpt.Epoch)
+		if err != nil {
+			return err
+		}
 		justifiedRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(s.justifiedCheckpt.Root))
 		anc, err := s.ancestor(ctx, justifiedRoot[:], finalizedSlot)
 		if err != nil {
@@ -335,7 +345,11 @@ func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk *ethpb.
 	parentRoot := bytesutil.ToBytes32(blk.ParentRoot)
 	slot := blk.Slot
 	// Fork choice only matters from last finalized slot.
-	higherThanFinalized := slot > helpers.StartSlot(s.finalizedCheckpt.Epoch)
+	fSlot, err := helpers.StartSlot(s.finalizedCheckpt.Epoch)
+	if err != nil {
+		return err
+	}
+	higherThanFinalized := slot > fSlot
 	// As long as parent node is not in fork choice store, and parent node is in DB.
 	for !s.forkChoiceStore.HasNode(parentRoot) && s.beaconDB.HasBlock(ctx, parentRoot) && higherThanFinalized {
 		b, err := s.beaconDB.Block(ctx, parentRoot)
@@ -346,7 +360,7 @@ func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk *ethpb.
 		pendingNodes = append(pendingNodes, b.Block)
 		parentRoot = bytesutil.ToBytes32(b.Block.ParentRoot)
 		slot = b.Block.Slot
-		higherThanFinalized = slot > helpers.StartSlot(s.finalizedCheckpt.Epoch)
+		higherThanFinalized = slot > fSlot
 	}
 
 	// Insert parent nodes to fork choice store in reverse order.
diff --git a/beacon-chain/core/epoch/precompute/justification_finalization.go b/beacon-chain/core/epoch/precompute/justification_finalization.go
index a043aea2ad..623a107b9d 100644
--- a/beacon-chain/core/epoch/precompute/justification_finalization.go
+++ b/beacon-chain/core/epoch/precompute/justification_finalization.go
@@ -49,7 +49,11 @@ import (
 //    if all(bits[0:2]) and old_current_justified_checkpoint.epoch + 1 == current_epoch:
 //        state.finalized_checkpoint = old_current_justified_checkpoint
 func ProcessJustificationAndFinalizationPreCompute(state *stateTrie.BeaconState, pBal *Balance) (*stateTrie.BeaconState, error) {
-	if state.Slot() <= helpers.StartSlot(2) {
+	canProcessSlot, err := helpers.StartSlot(2 /*epoch*/)
+	if err != nil {
+		return nil, err
+	}
+	if state.Slot() <= canProcessSlot {
 		return state, nil
 	}
 
diff --git a/beacon-chain/core/helpers/block.go b/beacon-chain/core/helpers/block.go
index a43618d534..2eed345c3b 100644
--- a/beacon-chain/core/helpers/block.go
+++ b/beacon-chain/core/helpers/block.go
@@ -32,5 +32,9 @@ func BlockRootAtSlot(state *stateTrie.BeaconState, slot uint64) ([]byte, error)
 //    """
 //    return get_block_root_at_slot(state, compute_start_slot_at_epoch(epoch))
 func BlockRoot(state *stateTrie.BeaconState, epoch uint64) ([]byte, error) {
-	return BlockRootAtSlot(state, StartSlot(epoch))
+	s, err := StartSlot(epoch)
+	if err != nil {
+		return nil, err
+	}
+	return BlockRootAtSlot(state, s)
 }
diff --git a/beacon-chain/core/helpers/committee.go b/beacon-chain/core/helpers/committee.go
index 21a4d19c3a..51e842e41b 100644
--- a/beacon-chain/core/helpers/committee.go
+++ b/beacon-chain/core/helpers/committee.go
@@ -200,7 +200,10 @@ func CommitteeAssignments(
 	// We determine the slots in which proposers are supposed to act.
 	// Some validators may need to propose multiple times per epoch, so
 	// we use a map of proposer idx -> []slot to keep track of this possibility.
-	startSlot := StartSlot(epoch)
+	startSlot, err := StartSlot(epoch)
+	if err != nil {
+		return nil, nil, err
+	}
 	proposerIndexToSlots := make(map[uint64][]uint64, params.BeaconConfig().SlotsPerEpoch)
 	for slot := startSlot; slot < startSlot+params.BeaconConfig().SlotsPerEpoch; slot++ {
 		// Skip proposer assignment for genesis slot.
@@ -380,7 +383,10 @@ func precomputeProposerIndices(state *stateTrie.BeaconState, activeIndices []uin
 	if err != nil {
 		return nil, errors.Wrap(err, "could not generate seed")
 	}
-	slot := StartSlot(e)
+	slot, err := StartSlot(e)
+	if err != nil {
+		return nil, err
+	}
 	for i := uint64(0); i < params.BeaconConfig().SlotsPerEpoch; i++ {
 		seedWithSlot := append(seed[:], bytesutil.Bytes8(slot+i)...)
 		seedWithSlotHash := hashFunc(seedWithSlot)
diff --git a/beacon-chain/core/helpers/committee_test.go b/beacon-chain/core/helpers/committee_test.go
index bbc3b52c78..2de0ae0d10 100644
--- a/beacon-chain/core/helpers/committee_test.go
+++ b/beacon-chain/core/helpers/committee_test.go
@@ -230,8 +230,10 @@ func TestCommitteeAssignments_EverySlotHasMin1Proposer(t *testing.T) {
 		}
 	}
 	assert.Equal(t, params.BeaconConfig().SlotsPerEpoch, uint64(len(slotsWithProposers)), "Unexpected slots")
-	startSlot := StartSlot(epoch)
-	endSlot := StartSlot(epoch + 1)
+	startSlot, err := StartSlot(epoch)
+	require.NoError(t, err)
+	endSlot, err := StartSlot(epoch + 1)
+	require.NoError(t, err)
 	for i := startSlot; i < endSlot; i++ {
 		hasProposer := slotsWithProposers[i]
 		assert.Equal(t, true, hasProposer, "Expected every slot in epoch 1 to have a proposer, slot %d did not", i)
@@ -390,7 +392,7 @@ func TestUpdateCommitteeCache_CanUpdate(t *testing.T) {
 	seed, err := Seed(state, epoch, params.BeaconConfig().DomainBeaconAttester)
 	require.NoError(t, err)
 
-	indices, err = committeeCache.Committee(StartSlot(epoch), seed, idx)
+	indices, err = committeeCache.Committee(epoch*params.BeaconConfig().SlotsPerEpoch, seed, idx)
 	require.NoError(t, err)
 	assert.Equal(t, params.BeaconConfig().TargetCommitteeSize, uint64(len(indices)), "Did not save correct indices lengths")
 }
diff --git a/beacon-chain/core/helpers/slot_epoch.go b/beacon-chain/core/helpers/slot_epoch.go
index 323cbe0502..38484b5356 100644
--- a/beacon-chain/core/helpers/slot_epoch.go
+++ b/beacon-chain/core/helpers/slot_epoch.go
@@ -1,8 +1,10 @@
 package helpers
 
 import (
+	"errors"
 	"fmt"
 	"math"
+	"math/bits"
 	"time"
 
 	stateTrie "github.com/prysmaticlabs/prysm/beacon-chain/state"
@@ -72,9 +74,13 @@ func NextEpoch(state *stateTrie.BeaconState) uint64 {
 //    """
 //    Return the start slot of ``epoch``.
 //    """
-//    return Slot(epoch * SLOTS_PER_EPOCH
-func StartSlot(epoch uint64) uint64 {
-	return epoch * params.BeaconConfig().SlotsPerEpoch
+//    return Slot(epoch * SLOTS_PER_EPOCH)
+func StartSlot(epoch uint64) (uint64, error) {
+	overflows, slot := bits.Mul64(epoch, params.BeaconConfig().SlotsPerEpoch)
+	if overflows > 0 {
+		return slot, errors.New("start slot calculation overflows")
+	}
+	return slot, nil
 }
 
 // IsEpochStart returns true if the given slot number is an epoch starting slot
@@ -91,7 +97,7 @@ func IsEpochEnd(slot uint64) bool {
 
 // SlotsSinceEpochStarts returns number of slots since the start of the epoch.
 func SlotsSinceEpochStarts(slot uint64) uint64 {
-	return slot - StartSlot(SlotToEpoch(slot))
+	return slot % params.BeaconConfig().SlotsPerEpoch
 }
 
 // VerifySlotTime validates the input slot is not from the future.
diff --git a/beacon-chain/core/helpers/slot_epoch_test.go b/beacon-chain/core/helpers/slot_epoch_test.go
index 581d703193..f31c37b935 100644
--- a/beacon-chain/core/helpers/slot_epoch_test.go
+++ b/beacon-chain/core/helpers/slot_epoch_test.go
@@ -86,14 +86,24 @@ func TestEpochStartSlot_OK(t *testing.T) {
 	tests := []struct {
 		epoch     uint64
 		startSlot uint64
+		error     bool
 	}{
-		{epoch: 0, startSlot: 0 * params.BeaconConfig().SlotsPerEpoch},
-		{epoch: 1, startSlot: 1 * params.BeaconConfig().SlotsPerEpoch},
-		{epoch: 10, startSlot: 10 * params.BeaconConfig().SlotsPerEpoch},
+		{epoch: 0, startSlot: 0 * params.BeaconConfig().SlotsPerEpoch, error: false},
+		{epoch: 1, startSlot: 1 * params.BeaconConfig().SlotsPerEpoch, error: false},
+		{epoch: 10, startSlot: 10 * params.BeaconConfig().SlotsPerEpoch, error: false},
+		{epoch: 1 << 58, startSlot: 1 << 63, error: false},
+		{epoch: 1 << 59, startSlot: 1 << 63, error: true},
+		{epoch: 1 << 60, startSlot: 1 << 63, error: true},
 	}
 	for _, tt := range tests {
 		state := &pb.BeaconState{Slot: tt.epoch}
-		assert.Equal(t, tt.startSlot, StartSlot(tt.epoch), "StartSlot(%d)", state.Slot)
+		ss, err := StartSlot(tt.epoch)
+		if !tt.error {
+			require.NoError(t, err)
+			assert.Equal(t, tt.startSlot, ss, "StartSlot(%d)", state.Slot)
+		} else {
+			require.ErrorContains(t, "start slot calculation overflow", err)
+		}
 	}
 }
 
diff --git a/beacon-chain/db/kv/blocks.go b/beacon-chain/db/kv/blocks.go
index 316fe47c00..ecba70e394 100644
--- a/beacon-chain/db/kv/blocks.go
+++ b/beacon-chain/db/kv/blocks.go
@@ -333,7 +333,7 @@ func getBlockRootsByFilter(ctx context.Context, tx *bolt.Tx, f *filters.QueryFil
 
 	// We retrieve block roots that match a filter criteria of slot ranges, if specified.
 	filtersMap := f.Filters()
-	rootsBySlotRange := fetchBlockRootsBySlotRange(
+	rootsBySlotRange, err := fetchBlockRootsBySlotRange(
 		ctx,
 		tx.Bucket(blockSlotIndicesBucket),
 		filtersMap[filters.StartSlot],
@@ -342,6 +342,9 @@ func getBlockRootsByFilter(ctx context.Context, tx *bolt.Tx, f *filters.QueryFil
 		filtersMap[filters.EndEpoch],
 		filtersMap[filters.SlotStep],
 	)
+	if err != nil {
+		return nil, err
+	}
 
 	// Once we have a list of block roots that correspond to each
 	// lookup index, we find the intersection across all of them and use
@@ -378,7 +381,7 @@ func fetchBlockRootsBySlotRange(
 	startEpochEncoded interface{},
 	endEpochEncoded interface{},
 	slotStepEncoded interface{},
-) [][]byte {
+) ([][]byte, error) {
 	ctx, span := trace.StartSpan(ctx, "BeaconDB.fetchBlockRootsBySlotRange")
 	defer span.End()
 
@@ -395,9 +398,17 @@ func fetchBlockRootsBySlotRange(
 	}
 	startEpoch, startEpochOk := startEpochEncoded.(uint64)
 	endEpoch, endEpochOk := endEpochEncoded.(uint64)
+	var err error
 	if startEpochOk && endEpochOk {
-		startSlot = helpers.StartSlot(startEpoch)
-		endSlot = helpers.StartSlot(endEpoch) + params.BeaconConfig().SlotsPerEpoch - 1
+		startSlot, err = helpers.StartSlot(startEpoch)
+		if err != nil {
+			return nil, err
+		}
+		endSlot, err = helpers.StartSlot(endEpoch)
+		if err != nil {
+			return nil, err
+		}
+		endSlot = endSlot + params.BeaconConfig().SlotsPerEpoch - 1
 	}
 	min := bytesutil.Uint64ToBytesBigEndian(startSlot)
 	max := bytesutil.Uint64ToBytesBigEndian(endSlot)
@@ -431,7 +442,7 @@ func fetchBlockRootsBySlotRange(
 		}
 		roots = append(roots, splitRoots...)
 	}
-	return roots
+	return roots, nil
 }
 
 // createBlockIndicesFromBlock takes in a beacon block and returns
diff --git a/beacon-chain/operations/slashings/BUILD.bazel b/beacon-chain/operations/slashings/BUILD.bazel
index c7e1729820..aa1e80f2fd 100644
--- a/beacon-chain/operations/slashings/BUILD.bazel
+++ b/beacon-chain/operations/slashings/BUILD.bazel
@@ -37,7 +37,6 @@ go_test(
     ],
     embed = [":go_default_library"],
     deps = [
-        "//beacon-chain/core/helpers:go_default_library",
         "//beacon-chain/state:go_default_library",
         "//shared/bls:go_default_library",
         "//shared/params:go_default_library",
diff --git a/beacon-chain/operations/slashings/service_attester_test.go b/beacon-chain/operations/slashings/service_attester_test.go
index ef099cfd1b..078fd8a720 100644
--- a/beacon-chain/operations/slashings/service_attester_test.go
+++ b/beacon-chain/operations/slashings/service_attester_test.go
@@ -9,7 +9,6 @@ import (
 	"github.com/prysmaticlabs/prysm/shared/testutil/assert"
 
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
-	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/shared/params"
 	"github.com/prysmaticlabs/prysm/shared/testutil"
 	"github.com/prysmaticlabs/prysm/shared/testutil/require"
@@ -88,7 +87,7 @@ func TestPool_InsertAttesterSlashing(t *testing.T) {
 		}
 		slashings[i] = sl
 	}
-	require.NoError(t, beaconState.SetSlot(helpers.StartSlot(1)))
+	require.NoError(t, beaconState.SetSlot(params.BeaconConfig().SlotsPerEpoch))
 
 	// We mark the following validators with some preconditions.
 	exitedVal, err := beaconState.ValidatorAtIndex(uint64(2))
diff --git a/beacon-chain/operations/slashings/service_proposer_test.go b/beacon-chain/operations/slashings/service_proposer_test.go
index d841c55489..b45b737f91 100644
--- a/beacon-chain/operations/slashings/service_proposer_test.go
+++ b/beacon-chain/operations/slashings/service_proposer_test.go
@@ -5,7 +5,6 @@ import (
 	"testing"
 
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
-	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/shared/params"
 	"github.com/prysmaticlabs/prysm/shared/testutil"
 	"github.com/prysmaticlabs/prysm/shared/testutil/assert"
@@ -41,7 +40,7 @@ func TestPool_InsertProposerSlashing(t *testing.T) {
 		slashings[i] = sl
 	}
 
-	require.NoError(t, beaconState.SetSlot(helpers.StartSlot(1)))
+	require.NoError(t, beaconState.SetSlot(params.BeaconConfig().SlotsPerEpoch))
 
 	// We mark the following validators with some preconditions.
 	exitedVal, err := beaconState.ValidatorAtIndex(uint64(2))
diff --git a/beacon-chain/p2p/peers/BUILD.bazel b/beacon-chain/p2p/peers/BUILD.bazel
index 3d74227962..8002097007 100644
--- a/beacon-chain/p2p/peers/BUILD.bazel
+++ b/beacon-chain/p2p/peers/BUILD.bazel
@@ -17,6 +17,7 @@ go_library(
         "//beacon-chain/flags:go_default_library",
         "//proto/beacon/p2p/v1:go_default_library",
         "//shared/featureconfig:go_default_library",
+        "//shared/params:go_default_library",
         "//shared/rand:go_default_library",
         "//shared/roughtime:go_default_library",
         "@com_github_ethereum_go_ethereum//p2p/enr:go_default_library",
diff --git a/beacon-chain/p2p/peers/status.go b/beacon-chain/p2p/peers/status.go
index b5b6431f3b..55ec9f7fae 100644
--- a/beacon-chain/p2p/peers/status.go
+++ b/beacon-chain/p2p/peers/status.go
@@ -34,6 +34,7 @@ import (
 	"github.com/prysmaticlabs/go-bitfield"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
+	"github.com/prysmaticlabs/prysm/shared/params"
 	"github.com/prysmaticlabs/prysm/shared/roughtime"
 )
 
@@ -489,7 +490,7 @@ func (p *Status) BestNonFinalized(minPeers int, ourFinalizedEpoch uint64) (uint6
 	pidHead := make(map[peer.ID]uint64, len(connected))
 	potentialPIDs := make([]peer.ID, 0, len(connected))
 
-	ourFinalizedSlot := helpers.StartSlot(ourFinalizedEpoch)
+	ourFinalizedSlot := ourFinalizedEpoch * params.BeaconConfig().SlotsPerEpoch
 	for _, pid := range connected {
 		peerChainState, err := p.ChainState(pid)
 		if err == nil && peerChainState != nil && peerChainState.HeadSlot > ourFinalizedSlot {
diff --git a/beacon-chain/rpc/beacon/assignments.go b/beacon-chain/rpc/beacon/assignments.go
index 68355871b2..1f443031b4 100644
--- a/beacon-chain/rpc/beacon/assignments.go
+++ b/beacon-chain/rpc/beacon/assignments.go
@@ -50,7 +50,11 @@ func (bs *Server) ListValidatorAssignments(
 		)
 	}
 
-	requestedState, err := bs.StateGen.StateBySlot(ctx, helpers.StartSlot(requestedEpoch))
+	startSlot, err := helpers.StartSlot(requestedEpoch)
+	if err != nil {
+		return nil, err
+	}
+	requestedState, err := bs.StateGen.StateBySlot(ctx, startSlot)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "Could not retrieve archived state for epoch %d: %v", requestedEpoch, err)
 	}
diff --git a/beacon-chain/rpc/beacon/attestations.go b/beacon-chain/rpc/beacon/attestations.go
index 6524cbaac5..3c8941dd57 100644
--- a/beacon-chain/rpc/beacon/attestations.go
+++ b/beacon-chain/rpc/beacon/attestations.go
@@ -295,7 +295,11 @@ func (bs *Server) StreamIndexedAttestations(
 			}
 			// We use the retrieved committees for the epoch to convert all attestations
 			// into indexed form effectively.
-			startSlot := helpers.StartSlot(targetEpoch)
+			startSlot, err := helpers.StartSlot(targetEpoch)
+			if err != nil {
+				log.Error(err)
+				continue
+			}
 			endSlot := startSlot + params.BeaconConfig().SlotsPerEpoch
 			for _, att := range aggAtts {
 				// Out of range check, the attestation slot cannot be greater
diff --git a/beacon-chain/rpc/beacon/attestations_test.go b/beacon-chain/rpc/beacon/attestations_test.go
index 625d77c7cd..30f0532e58 100644
--- a/beacon-chain/rpc/beacon/attestations_test.go
+++ b/beacon-chain/rpc/beacon/attestations_test.go
@@ -658,7 +658,8 @@ func TestServer_ListIndexedAttestations_OldEpoch(t *testing.T) {
 	count := params.BeaconConfig().SlotsPerEpoch
 	atts := make([]*ethpb.Attestation, 0, count)
 	epoch := uint64(50)
-	startSlot := helpers.StartSlot(epoch)
+	startSlot, err := helpers.StartSlot(epoch)
+	require.NoError(t, err)
 
 	for i := startSlot; i < count; i++ {
 		blockExample := &ethpb.SignedBeaconBlock{
@@ -714,9 +715,9 @@ func TestServer_ListIndexedAttestations_OldEpoch(t *testing.T) {
 		},
 		StateGen: stategen.New(db, sc),
 	}
-	err := db.SaveStateSummary(ctx, &pbp2p.StateSummary{
+	err = db.SaveStateSummary(ctx, &pbp2p.StateSummary{
 		Root: blockRoot[:],
-		Slot: helpers.StartSlot(epoch),
+		Slot: epoch * params.BeaconConfig().SlotsPerEpoch,
 	})
 	require.NoError(t, err)
 	require.NoError(t, db.SaveState(ctx, state, bytesutil.ToBytes32([]byte("root"))))
@@ -916,7 +917,7 @@ func TestServer_StreamIndexedAttestations_OK(t *testing.T) {
 	epoch := uint64(0)
 	attesterSeed, err := helpers.Seed(headState, epoch, params.BeaconConfig().DomainBeaconAttester)
 	require.NoError(t, err)
-	committees, err := computeCommittees(helpers.StartSlot(epoch), activeIndices, attesterSeed)
+	committees, err := computeCommittees(epoch*params.BeaconConfig().SlotsPerEpoch, activeIndices, attesterSeed)
 	require.NoError(t, err)
 
 	count := params.BeaconConfig().SlotsPerEpoch
diff --git a/beacon-chain/rpc/beacon/blocks.go b/beacon-chain/rpc/beacon/blocks.go
index 0ca472da1d..f1ef72e93c 100644
--- a/beacon-chain/rpc/beacon/blocks.go
+++ b/beacon-chain/rpc/beacon/blocks.go
@@ -298,17 +298,29 @@ func (bs *Server) chainHeadRetrieval(ctx context.Context) (*ethpb.ChainHead, err
 		}
 	}
 
+	fSlot, err := helpers.StartSlot(finalizedCheckpoint.Epoch)
+	if err != nil {
+		return nil, err
+	}
+	jSlot, err := helpers.StartSlot(justifiedCheckpoint.Epoch)
+	if err != nil {
+		return nil, err
+	}
+	pjSlot, err := helpers.StartSlot(prevJustifiedCheckpoint.Epoch)
+	if err != nil {
+		return nil, err
+	}
 	return &ethpb.ChainHead{
 		HeadSlot:                   headBlock.Block.Slot,
 		HeadEpoch:                  helpers.SlotToEpoch(headBlock.Block.Slot),
 		HeadBlockRoot:              headBlockRoot[:],
-		FinalizedSlot:              helpers.StartSlot(finalizedCheckpoint.Epoch),
+		FinalizedSlot:              fSlot,
 		FinalizedEpoch:             finalizedCheckpoint.Epoch,
 		FinalizedBlockRoot:         finalizedCheckpoint.Root,
-		JustifiedSlot:              helpers.StartSlot(justifiedCheckpoint.Epoch),
+		JustifiedSlot:              jSlot,
 		JustifiedEpoch:             justifiedCheckpoint.Epoch,
 		JustifiedBlockRoot:         justifiedCheckpoint.Root,
-		PreviousJustifiedSlot:      helpers.StartSlot(prevJustifiedCheckpoint.Epoch),
+		PreviousJustifiedSlot:      pjSlot,
 		PreviousJustifiedEpoch:     prevJustifiedCheckpoint.Epoch,
 		PreviousJustifiedBlockRoot: prevJustifiedCheckpoint.Root,
 	}, nil
diff --git a/beacon-chain/rpc/beacon/blocks_test.go b/beacon-chain/rpc/beacon/blocks_test.go
index d0dc80ad61..429e397a92 100644
--- a/beacon-chain/rpc/beacon/blocks_test.go
+++ b/beacon-chain/rpc/beacon/blocks_test.go
@@ -404,7 +404,9 @@ func TestServer_GetChainHead(t *testing.T) {
 	require.NoError(t, err)
 
 	b := testutil.NewBeaconBlock()
-	b.Block.Slot = helpers.StartSlot(s.PreviousJustifiedCheckpoint().Epoch) + 1
+	b.Block.Slot, err = helpers.StartSlot(s.PreviousJustifiedCheckpoint().Epoch)
+	require.NoError(t, err)
+	b.Block.Slot++
 	bs := &Server{
 		BeaconDB:    db,
 		HeadFetcher: &chainMock.ChainService{Block: b, State: s},
@@ -492,7 +494,8 @@ func TestServer_StreamChainHead_OnHeadUpdated(t *testing.T) {
 	require.NoError(t, err)
 
 	b := testutil.NewBeaconBlock()
-	b.Block.Slot = helpers.StartSlot(s.PreviousJustifiedCheckpoint().Epoch) + 1
+	b.Block.Slot, err = helpers.StartSlot(s.PreviousJustifiedCheckpoint().Epoch)
+
 	hRoot, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)
 
diff --git a/beacon-chain/rpc/beacon/committees.go b/beacon-chain/rpc/beacon/committees.go
index 2c4151f478..0e09c311d0 100644
--- a/beacon-chain/rpc/beacon/committees.go
+++ b/beacon-chain/rpc/beacon/committees.go
@@ -20,12 +20,15 @@ func (bs *Server) ListBeaconCommittees(
 	ctx context.Context,
 	req *ethpb.ListCommitteesRequest,
 ) (*ethpb.BeaconCommittees, error) {
-
 	currentSlot := bs.GenesisTimeFetcher.CurrentSlot()
 	var requestedSlot uint64
 	switch q := req.QueryFilter.(type) {
 	case *ethpb.ListCommitteesRequest_Epoch:
-		requestedSlot = helpers.StartSlot(q.Epoch)
+		startSlot, err := helpers.StartSlot(q.Epoch)
+		if err != nil {
+			return nil, err
+		}
+		requestedSlot = startSlot
 	case *ethpb.ListCommitteesRequest_Genesis:
 		requestedSlot = 0
 	default:
@@ -64,7 +67,10 @@ func (bs *Server) retrieveCommitteesForEpoch(
 	ctx context.Context,
 	epoch uint64,
 ) (map[uint64]*ethpb.BeaconCommittees_CommitteesList, []uint64, error) {
-	startSlot := helpers.StartSlot(epoch)
+	startSlot, err := helpers.StartSlot(epoch)
+	if err != nil {
+		return nil, nil, err
+	}
 	requestedState, err := bs.StateGen.StateBySlot(ctx, startSlot)
 	if err != nil {
 		return nil, nil, status.Error(codes.Internal, "Could not get state")
@@ -111,7 +117,10 @@ func (bs *Server) retrieveCommitteesForRoot(
 		return nil, nil, status.Error(codes.Internal, "Could not get active indices")
 	}
 
-	startSlot := helpers.StartSlot(epoch)
+	startSlot, err := helpers.StartSlot(epoch)
+	if err != nil {
+		return nil, nil, err
+	}
 	committeesListsBySlot, err := computeCommittees(startSlot, activeIndices, seed)
 	if err != nil {
 		return nil, nil, status.Errorf(
diff --git a/beacon-chain/rpc/beacon/committees_test.go b/beacon-chain/rpc/beacon/committees_test.go
index 1ac88ec5c6..5e15b5b2ff 100644
--- a/beacon-chain/rpc/beacon/committees_test.go
+++ b/beacon-chain/rpc/beacon/committees_test.go
@@ -106,7 +106,8 @@ func TestServer_ListBeaconCommittees_PreviousEpoch(t *testing.T) {
 	require.NoError(t, err)
 	attesterSeed, err := helpers.Seed(headState, 1, params.BeaconConfig().DomainBeaconAttester)
 	require.NoError(t, err)
-	startSlot := helpers.StartSlot(1)
+	startSlot, err := helpers.StartSlot(1)
+	require.NoError(t, err)
 	wanted, err := computeCommittees(startSlot, activeIndices, attesterSeed)
 	require.NoError(t, err)
 
diff --git a/beacon-chain/rpc/beacon/validators.go b/beacon-chain/rpc/beacon/validators.go
index d43951afff..b7993ab486 100644
--- a/beacon-chain/rpc/beacon/validators.go
+++ b/beacon-chain/rpc/beacon/validators.go
@@ -56,7 +56,11 @@ func (bs *Server) ListValidatorBalances(
 	res := make([]*ethpb.ValidatorBalances_Balance, 0)
 	filtered := map[uint64]bool{} // Track filtered validators to prevent duplication in the response.
 
-	requestedState, err := bs.StateGen.StateBySlot(ctx, helpers.StartSlot(requestedEpoch))
+	startSlot, err := helpers.StartSlot(requestedEpoch)
+	if err != nil {
+		return nil, err
+	}
+	requestedState, err := bs.StateGen.StateBySlot(ctx, startSlot)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "Could not get state")
 	}
@@ -189,7 +193,11 @@ func (bs *Server) ListValidators(
 	var reqState *statetrie.BeaconState
 	var err error
 	if requestedEpoch != currentEpoch {
-		reqState, err = bs.StateGen.StateBySlot(ctx, helpers.StartSlot(requestedEpoch))
+		s, err := helpers.StartSlot(requestedEpoch)
+		if err != nil {
+			return nil, err
+		}
+		reqState, err = bs.StateGen.StateBySlot(ctx, s)
 	} else {
 		reqState, err = bs.HeadFetcher.HeadState(ctx)
 	}
@@ -198,14 +206,18 @@ func (bs *Server) ListValidators(
 		return nil, status.Error(codes.Internal, "Could not get requested state")
 	}
 
-	if helpers.StartSlot(requestedEpoch) > reqState.Slot() {
+	s, err := helpers.StartSlot(requestedEpoch)
+	if err != nil {
+		return nil, err
+	}
+	if s > reqState.Slot() {
 		reqState = reqState.Copy()
-		reqState, err = state.ProcessSlots(ctx, reqState, helpers.StartSlot(requestedEpoch))
+		reqState, err = state.ProcessSlots(ctx, reqState, s)
 		if err != nil {
 			return nil, status.Errorf(
 				codes.Internal,
-				"Could not process slots up to %d: %v",
-				helpers.StartSlot(requestedEpoch),
+				"Could not process slots up to epoch %d: %v",
+				requestedEpoch,
 				err,
 			)
 		}
@@ -389,7 +401,11 @@ func (bs *Server) GetValidatorActiveSetChanges(
 	slashedIndices := make([]uint64, 0)
 	ejectedIndices := make([]uint64, 0)
 
-	requestedState, err := bs.StateGen.StateBySlot(ctx, helpers.StartSlot(requestedEpoch))
+	s, err := helpers.StartSlot(requestedEpoch)
+	if err != nil {
+		return nil, err
+	}
+	requestedState, err := bs.StateGen.StateBySlot(ctx, s)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "Could not get state: %v", err)
 	}
@@ -475,7 +491,11 @@ func (bs *Server) GetValidatorParticipation(
 	}
 	// Calculate the end slot of the next epoch.
 	// Ex: requested epoch 1, this gets slot 95.
-	nextEpochEndSlot := helpers.StartSlot(requestedEpoch+2) - 1
+	nextEpochEndSlot, err := helpers.StartSlot(requestedEpoch + 2)
+	if err != nil {
+		return nil, err
+	}
+	nextEpochEndSlot--
 	requestedState, err := bs.StateGen.StateBySlot(ctx, nextEpochEndSlot)
 	if err != nil {
 		return nil, status.Error(codes.Internal, "Could not get state")
@@ -748,7 +768,11 @@ func (bs *Server) GetIndividualVotes(
 		)
 	}
 
-	requestedState, err := bs.StateGen.StateBySlot(ctx, helpers.StartSlot(req.Epoch))
+	s, err := helpers.StartSlot(req.Epoch)
+	if err != nil {
+		return nil, err
+	}
+	requestedState, err := bs.StateGen.StateBySlot(ctx, s)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "Could not retrieve archived state for epoch %d: %v", req.Epoch, err)
 	}
diff --git a/beacon-chain/rpc/beacon/validators_test.go b/beacon-chain/rpc/beacon/validators_test.go
index 89cbd24723..e1e59d0420 100644
--- a/beacon-chain/rpc/beacon/validators_test.go
+++ b/beacon-chain/rpc/beacon/validators_test.go
@@ -883,7 +883,7 @@ func TestServer_ListValidators_FromOldEpoch(t *testing.T) {
 	}
 
 	st := testutil.NewBeaconState()
-	require.NoError(t, st.SetSlot(helpers.StartSlot(30)))
+	require.NoError(t, st.SetSlot(30*params.BeaconConfig().SlotsPerEpoch))
 	require.NoError(t, st.SetValidators(validators))
 	b := testutil.NewBeaconBlock()
 	require.NoError(t, db.SaveBlock(ctx, b))
@@ -1249,7 +1249,7 @@ func TestServer_GetValidatorQueue_ExitedValidatorLeavesQueue(t *testing.T) {
 
 	// Now, we move the state.slot past the exit epoch of the validator, and now
 	// the validator should no longer exist in the queue.
-	require.NoError(t, headState.SetSlot(helpers.StartSlot(validators[1].ExitEpoch+1)))
+	require.NoError(t, headState.SetSlot((validators[1].ExitEpoch+1)*params.BeaconConfig().SlotsPerEpoch))
 	res, err = bs.GetValidatorQueue(context.Background(), &ptypes.Empty{})
 	require.NoError(t, err)
 	assert.Equal(t, 0, len(res.ExitPublicKeys))
@@ -1450,7 +1450,7 @@ func TestGetValidatorPerformance_OK(t *testing.T) {
 	ctx := context.Background()
 	epoch := uint64(1)
 	headState := testutil.NewBeaconState()
-	require.NoError(t, headState.SetSlot(helpers.StartSlot(epoch+1)))
+	require.NoError(t, headState.SetSlot((epoch+1)*params.BeaconConfig().SlotsPerEpoch))
 	atts := make([]*pb.PendingAttestation, 3)
 	for i := 0; i < len(atts); i++ {
 		atts[i] = &pb.PendingAttestation{
@@ -1527,7 +1527,7 @@ func TestGetValidatorPerformance_Indices(t *testing.T) {
 	defaultBal := params.BeaconConfig().MaxEffectiveBalance
 	extraBal := params.BeaconConfig().MaxEffectiveBalance + params.BeaconConfig().GweiPerEth
 	headState := testutil.NewBeaconState()
-	require.NoError(t, headState.SetSlot(helpers.StartSlot(epoch+1)))
+	require.NoError(t, headState.SetSlot((epoch+1)*params.BeaconConfig().SlotsPerEpoch))
 	balances := []uint64{defaultBal, extraBal, extraBal + params.BeaconConfig().GweiPerEth}
 	require.NoError(t, headState.SetBalances(balances))
 	publicKey1 := bytesutil.ToBytes48([]byte{1})
@@ -1597,7 +1597,7 @@ func TestGetValidatorPerformance_IndicesPubkeys(t *testing.T) {
 	defaultBal := params.BeaconConfig().MaxEffectiveBalance
 	extraBal := params.BeaconConfig().MaxEffectiveBalance + params.BeaconConfig().GweiPerEth
 	headState := testutil.NewBeaconState()
-	require.NoError(t, headState.SetSlot(helpers.StartSlot(epoch+1)))
+	require.NoError(t, headState.SetSlot((epoch+1)*params.BeaconConfig().SlotsPerEpoch))
 	balances := []uint64{defaultBal, extraBal, extraBal + params.BeaconConfig().GweiPerEth}
 	require.NoError(t, headState.SetBalances(balances))
 	publicKey1 := bytesutil.ToBytes48([]byte{1})
diff --git a/beacon-chain/rpc/validator/assignments.go b/beacon-chain/rpc/validator/assignments.go
index e5c41852a7..175af8d778 100644
--- a/beacon-chain/rpc/validator/assignments.go
+++ b/beacon-chain/rpc/validator/assignments.go
@@ -113,7 +113,11 @@ func (vs *Server) duties(ctx context.Context, req *ethpb.DutiesRequest) (*ethpb.
 	}
 
 	// Advance state with empty transitions up to the requested epoch start slot.
-	if epochStartSlot := helpers.StartSlot(req.Epoch); s.Slot() < epochStartSlot {
+	epochStartSlot, err := helpers.StartSlot(req.Epoch)
+	if err != nil {
+		return nil, err
+	}
+	if s.Slot() < epochStartSlot {
 		s, err = state.ProcessSlots(ctx, s, epochStartSlot)
 		if err != nil {
 			return nil, status.Errorf(codes.Internal, "Could not process slots up to %d: %v", epochStartSlot, err)
diff --git a/beacon-chain/rpc/validator/assignments_test.go b/beacon-chain/rpc/validator/assignments_test.go
index ad89e0cab1..c6ed57e6a0 100644
--- a/beacon-chain/rpc/validator/assignments_test.go
+++ b/beacon-chain/rpc/validator/assignments_test.go
@@ -14,7 +14,6 @@ import (
 	"github.com/prysmaticlabs/prysm/beacon-chain/cache/depositcache"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/feed"
 	statefeed "github.com/prysmaticlabs/prysm/beacon-chain/core/feed/state"
-	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/state"
 	dbutil "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
 	mockPOW "github.com/prysmaticlabs/prysm/beacon-chain/powchain/testing"
@@ -380,7 +379,7 @@ func TestStreamDuties_OK_ChainReorg(t *testing.T) {
 	for sent := 0; sent == 0; {
 		sent = vs.StateNotifier.StateFeed().Send(&feed.Event{
 			Type: statefeed.Reorg,
-			Data: &statefeed.ReorgData{OldSlot: helpers.StartSlot(1), NewSlot: 0},
+			Data: &statefeed.ReorgData{OldSlot: params.BeaconConfig().SlotsPerEpoch, NewSlot: 0},
 		})
 	}
 	<-exitRoutine
diff --git a/beacon-chain/rpc/validator/attester.go b/beacon-chain/rpc/validator/attester.go
index 4652266c4a..c2cc19ed14 100644
--- a/beacon-chain/rpc/validator/attester.go
+++ b/beacon-chain/rpc/validator/attester.go
@@ -97,14 +97,17 @@ func (vs *Server) GetAttestationData(ctx context.Context, req *ethpb.Attestation
 	}
 
 	if helpers.CurrentEpoch(headState) < helpers.SlotToEpoch(req.Slot) {
-		headState, err = state.ProcessSlots(ctx, headState, helpers.StartSlot(helpers.SlotToEpoch(req.Slot)))
+		headState, err = state.ProcessSlots(ctx, headState, req.Slot)
 		if err != nil {
 			return nil, status.Errorf(codes.Internal, "Could not process slots up to %d: %v", req.Slot, err)
 		}
 	}
 
 	targetEpoch := helpers.CurrentEpoch(headState)
-	epochStartSlot := helpers.StartSlot(targetEpoch)
+	epochStartSlot, err := helpers.StartSlot(targetEpoch)
+	if err != nil {
+		return nil, err
+	}
 	targetRoot := make([]byte, 32)
 	if epochStartSlot == headState.Slot() {
 		targetRoot = headRoot[:]
diff --git a/beacon-chain/rpc/validator/attester_test.go b/beacon-chain/rpc/validator/attester_test.go
index 3f47102263..2f8097e09b 100644
--- a/beacon-chain/rpc/validator/attester_test.go
+++ b/beacon-chain/rpc/validator/attester_test.go
@@ -208,9 +208,13 @@ func TestAttestationDataAtSlot_HandlesFarAwayJustifiedEpoch(t *testing.T) {
 	block := testutil.NewBeaconBlock()
 	block.Block.Slot = 10000
 	epochBoundaryBlock := testutil.NewBeaconBlock()
-	epochBoundaryBlock.Block.Slot = helpers.StartSlot(helpers.SlotToEpoch(10000))
+	var err error
+	epochBoundaryBlock.Block.Slot, err = helpers.StartSlot(helpers.SlotToEpoch(10000))
+	require.NoError(t, err)
 	justifiedBlock := testutil.NewBeaconBlock()
-	justifiedBlock.Block.Slot = helpers.StartSlot(helpers.SlotToEpoch(1500)) - 2 // Imagine two skip block
+	justifiedBlock.Block.Slot, err = helpers.StartSlot(helpers.SlotToEpoch(1500))
+	require.NoError(t, err)
+	justifiedBlock.Block.Slot = justifiedBlock.Block.Slot - 2 // Imagine two skip block
 	blockRoot, err := block.Block.HashTreeRoot()
 	require.NoError(t, err, "Could not hash beacon block")
 	justifiedBlockRoot, err := justifiedBlock.Block.HashTreeRoot()
diff --git a/beacon-chain/rpc/validator/exit.go b/beacon-chain/rpc/validator/exit.go
index 37603b981a..8eb9f3e827 100644
--- a/beacon-chain/rpc/validator/exit.go
+++ b/beacon-chain/rpc/validator/exit.go
@@ -33,6 +33,7 @@ func (vs *Server) ProposeExit(ctx context.Context, req *ethpb.SignedVoluntaryExi
 	if err != nil {
 		return nil, status.Error(codes.InvalidArgument, "validator index exceeds validator set length")
 	}
+
 	if err := blocks.VerifyExitAndSignature(val, s.Slot(), s.Fork(), req, s.GenesisValidatorRoot()); err != nil {
 		return nil, status.Error(codes.InvalidArgument, err.Error())
 	}
diff --git a/beacon-chain/sync/initial-sync/blocks_fetcher.go b/beacon-chain/sync/initial-sync/blocks_fetcher.go
index 432f6f7874..68f0dbe804 100644
--- a/beacon-chain/sync/initial-sync/blocks_fetcher.go
+++ b/beacon-chain/sync/initial-sync/blocks_fetcher.go
@@ -265,7 +265,7 @@ func (f *blocksFetcher) handleRequest(ctx context.Context, start, count uint64)
 
 	// Short circuit start far exceeding the highest finalized epoch in some infinite loop.
 	if f.mode == modeStopOnFinalizedEpoch {
-		highestFinalizedSlot := helpers.StartSlot(targetEpoch + 1)
+		highestFinalizedSlot := (targetEpoch + 1) * params.BeaconConfig().SlotsPerEpoch
 		if start > highestFinalizedSlot {
 			response.err = fmt.Errorf("%v, slot: %d, highest finalized slot: %d",
 				errSlotIsTooHigh, start, highestFinalizedSlot)
diff --git a/beacon-chain/sync/initial-sync/blocks_fetcher_utils.go b/beacon-chain/sync/initial-sync/blocks_fetcher_utils.go
index 8b8f293a10..620d941589 100644
--- a/beacon-chain/sync/initial-sync/blocks_fetcher_utils.go
+++ b/beacon-chain/sync/initial-sync/blocks_fetcher_utils.go
@@ -94,7 +94,10 @@ func (f *blocksFetcher) nonSkippedSlotAfter(ctx context.Context, slot uint64) (u
 	// Quickly find the close enough epoch where a non-empty slot definitely exists.
 	// Only single random slot per epoch is checked - allowing to move forward relatively quickly.
 	slot = slot + nonSkippedSlotsFullSearchEpochs*slotsPerEpoch
-	upperBoundSlot := helpers.StartSlot(targetEpoch + 1)
+	upperBoundSlot, err := helpers.StartSlot(targetEpoch + 1)
+	if err != nil {
+		return 0, err
+	}
 	for ind := slot + 1; ind < upperBoundSlot; ind += (slotsPerEpoch * slotsPerEpoch) / 2 {
 		start := ind + uint64(f.rand.Intn(int(slotsPerEpoch)))
 		nextSlot, err := fetch(peers[pidInd%len(peers)], start, slotsPerEpoch/2, slotsPerEpoch)
@@ -112,12 +115,19 @@ func (f *blocksFetcher) nonSkippedSlotAfter(ctx context.Context, slot uint64) (u
 	if upperBoundSlot > slotsPerEpoch {
 		upperBoundSlot -= slotsPerEpoch
 	}
-	upperBoundSlot = helpers.StartSlot(helpers.SlotToEpoch(upperBoundSlot))
+	upperBoundSlot, err = helpers.StartSlot(helpers.SlotToEpoch(upperBoundSlot))
+	if err != nil {
+		return 0, err
+	}
 	nextSlot, err := fetch(peers[pidInd%len(peers)], upperBoundSlot, slotsPerEpoch*2, 1)
 	if err != nil {
 		return 0, err
 	}
-	if nextSlot < slot || helpers.StartSlot(targetEpoch+1) < nextSlot {
+	s, err := helpers.StartSlot(targetEpoch + 1)
+	if err != nil {
+		return 0, err
+	}
+	if nextSlot < slot || s < nextSlot {
 		return 0, errors.New("invalid range for non-skipped slot")
 	}
 	return nextSlot, nil
@@ -126,12 +136,12 @@ func (f *blocksFetcher) nonSkippedSlotAfter(ctx context.Context, slot uint64) (u
 // bestFinalizedSlot returns the highest finalized slot of the majority of connected peers.
 func (f *blocksFetcher) bestFinalizedSlot() uint64 {
 	finalizedEpoch, _ := f.p2p.Peers().BestFinalized(params.BeaconConfig().MaxPeersToSync, f.finalizationFetcher.FinalizedCheckpt().Epoch)
-	return helpers.StartSlot(finalizedEpoch)
+	return finalizedEpoch * params.BeaconConfig().SlotsPerEpoch
 }
 
 // bestNonFinalizedSlot returns the highest non-finalized slot of enough number of connected peers.
 func (f *blocksFetcher) bestNonFinalizedSlot() uint64 {
 	headEpoch := helpers.SlotToEpoch(f.headFetcher.HeadSlot())
 	targetEpoch, _ := f.p2p.Peers().BestNonFinalized(flags.Get().MinimumSyncPeers*2, headEpoch)
-	return helpers.StartSlot(targetEpoch)
+	return targetEpoch * params.BeaconConfig().SlotsPerEpoch
 }
diff --git a/beacon-chain/sync/initial-sync/round_robin.go b/beacon-chain/sync/initial-sync/round_robin.go
index f9c6c89c26..39463942ac 100644
--- a/beacon-chain/sync/initial-sync/round_robin.go
+++ b/beacon-chain/sync/initial-sync/round_robin.go
@@ -49,7 +49,10 @@ func (s *Service) roundRobinSync(genesis time.Time) error {
 
 	s.counter = ratecounter.NewRateCounter(counterSeconds * time.Second)
 	s.lastProcessedSlot = s.chain.HeadSlot()
-	highestFinalizedSlot := helpers.StartSlot(s.highestFinalizedEpoch() + 1)
+	highestFinalizedSlot, err := helpers.StartSlot(s.highestFinalizedEpoch() + 1)
+	if err != nil {
+		return err
+	}
 	queue := newBlocksQueue(ctx, &blocksQueueConfig{
 		p2p:                 s.p2p,
 		headFetcher:         s.chain,
diff --git a/beacon-chain/sync/validate_aggregate_proof.go b/beacon-chain/sync/validate_aggregate_proof.go
index 48e9c7daa9..64d691bc18 100644
--- a/beacon-chain/sync/validate_aggregate_proof.go
+++ b/beacon-chain/sync/validate_aggregate_proof.go
@@ -158,7 +158,11 @@ func (s *Service) validateAggregatedAtt(ctx context.Context, signed *ethpb.Signe
 
 	// Only advance state if different epoch as the committee can only change on an epoch transition.
 	if helpers.SlotToEpoch(attSlot) > helpers.SlotToEpoch(bs.Slot()) {
-		bs, err = state.ProcessSlots(ctx, bs, helpers.StartSlot(helpers.SlotToEpoch(attSlot)))
+		startSlot, err := helpers.StartSlot(helpers.SlotToEpoch(attSlot))
+		if err != nil {
+			return pubsub.ValidationIgnore
+		}
+		bs, err = state.ProcessSlots(ctx, bs, startSlot)
 		if err != nil {
 			traceutil.AnnotateError(span, err)
 			return pubsub.ValidationIgnore
diff --git a/beacon-chain/sync/validate_beacon_blocks.go b/beacon-chain/sync/validate_beacon_blocks.go
index 9eca339b3d..47ba857085 100644
--- a/beacon-chain/sync/validate_beacon_blocks.go
+++ b/beacon-chain/sync/validate_beacon_blocks.go
@@ -101,7 +101,11 @@ func (s *Service) validateBeaconBlockPubSub(ctx context.Context, pid peer.ID, ms
 		return pubsub.ValidationIgnore
 	}
 
-	if helpers.StartSlot(s.chain.FinalizedCheckpt().Epoch) >= blk.Block.Slot {
+	startSlot, err := helpers.StartSlot(s.chain.FinalizedCheckpt().Epoch)
+	if err != nil {
+		return pubsub.ValidationIgnore
+	}
+	if startSlot >= blk.Block.Slot {
 		log.Debug("Block slot older/equal than last finalized epoch start slot, rejecting it")
 		return pubsub.ValidationIgnore
 	}
diff --git a/validator/client/validator.go b/validator/client/validator.go
index 788fc1d85e..2d3ee3b3c8 100644
--- a/validator/client/validator.go
+++ b/validator/client/validator.go
@@ -352,13 +352,16 @@ func (v *validator) UpdateDuties(ctx context.Context, slot uint64) error {
 		return nil
 	}
 	// Set deadline to end of epoch.
-	ctx, cancel := context.WithDeadline(ctx, v.SlotDeadline(helpers.StartSlot(helpers.SlotToEpoch(slot)+1)))
+	ss, err := helpers.StartSlot(helpers.SlotToEpoch(slot) + 1)
+	if err != nil {
+		return err
+	}
+	ctx, cancel := context.WithDeadline(ctx, v.SlotDeadline(ss))
 	defer cancel()
 	ctx, span := trace.StartSpan(ctx, "validator.UpdateAssignments")
 	defer span.End()
 
 	var validatingKeys [][48]byte
-	var err error
 	if featureconfig.Get().EnableAccountsV2 {
 		validatingKeys, err = v.keyManagerV2.FetchValidatingPublicKeys(ctx)
 	} else {
@@ -644,7 +647,7 @@ func (v *validator) logDuties(slot uint64, duties []*ethpb.DutiesResponse_Duty)
 		attesterKeys[i] = make([]string, 0)
 	}
 	proposerKeys := make([]string, params.BeaconConfig().SlotsPerEpoch)
-	slotOffset := helpers.StartSlot(helpers.SlotToEpoch(slot))
+	slotOffset := slot - (slot % params.BeaconConfig().SlotsPerEpoch)
 
 	for _, duty := range duties {
 		if v.emitAccountMetrics {