diff --git a/pkg/core/transaction/attribute_test.go b/pkg/core/transaction/attribute_test.go
index b38c88181..f35a79732 100644
--- a/pkg/core/transaction/attribute_test.go
+++ b/pkg/core/transaction/attribute_test.go
@@ -52,14 +52,9 @@ func TestAttribute_EncodeBinary(t *testing.T) {
 			}
 			testserdes.EncodeDecodeBinary(t, attr, new(Attribute))
 		})
-		t.Run("bad format: too long", func(t *testing.T) {
-			bw := io.NewBufBinWriter()
-			bw.WriteVarBytes([]byte{1, 2, 3, 4, 5})
-			require.Error(t, testserdes.DecodeBinary(bw.Bytes(), new(NotValidBefore)))
-		})
 		t.Run("bad format: too short", func(t *testing.T) {
 			bw := io.NewBufBinWriter()
-			bw.WriteVarBytes([]byte{1, 2, 3})
+			bw.WriteBytes([]byte{1, 2, 3})
 			require.Error(t, testserdes.DecodeBinary(bw.Bytes(), new(NotValidBefore)))
 		})
 	})
@@ -96,14 +91,9 @@ func TestAttribute_EncodeBinary(t *testing.T) {
 			}
 			testserdes.EncodeDecodeBinary(t, attr, new(Attribute))
 		})
-		t.Run("negative: too long", func(t *testing.T) {
-			bw := io.NewBufBinWriter()
-			bw.WriteVarBytes(make([]byte, util.Uint256Size+1))
-			require.Error(t, testserdes.DecodeBinary(bw.Bytes(), new(Conflicts)))
-		})
 		t.Run("negative: bad uint256", func(t *testing.T) {
 			bw := io.NewBufBinWriter()
-			bw.WriteVarBytes(make([]byte, util.Uint256Size-1))
+			bw.WriteBytes(make([]byte, util.Uint256Size-1))
 			require.Error(t, testserdes.DecodeBinary(bw.Bytes(), new(Conflicts)))
 		})
 	})
@@ -117,14 +107,9 @@ func TestAttribute_EncodeBinary(t *testing.T) {
 			}
 			testserdes.EncodeDecodeBinary(t, attr, new(Attribute))
 		})
-		t.Run("bad format: too long", func(t *testing.T) {
-			bw := io.NewBufBinWriter()
-			bw.WriteVarBytes(make([]byte, 2))
-			require.Error(t, testserdes.DecodeBinary(bw.Bytes(), new(NotaryAssisted)))
-		})
 		t.Run("bad format: too short", func(t *testing.T) {
 			bw := io.NewBufBinWriter()
-			bw.WriteVarBytes([]byte{})
+			bw.WriteBytes([]byte{})
 			require.Error(t, testserdes.DecodeBinary(bw.Bytes(), new(NotaryAssisted)))
 		})
 	})
diff --git a/pkg/core/transaction/conflicts.go b/pkg/core/transaction/conflicts.go
index 77eff8c64..01b62e441 100644
--- a/pkg/core/transaction/conflicts.go
+++ b/pkg/core/transaction/conflicts.go
@@ -12,21 +12,12 @@ type Conflicts struct {
 
 // DecodeBinary implements the io.Serializable interface.
 func (c *Conflicts) DecodeBinary(br *io.BinReader) {
-	bytes := br.ReadVarBytes(util.Uint256Size)
-	if br.Err != nil {
-		return
-	}
-	hash, err := util.Uint256DecodeBytesBE(bytes)
-	if err != nil {
-		br.Err = err
-		return
-	}
-	c.Hash = hash
+	c.Hash.DecodeBinary(br)
 }
 
 // EncodeBinary implements the io.Serializable interface.
 func (c *Conflicts) EncodeBinary(w *io.BinWriter) {
-	w.WriteVarBytes(c.Hash.BytesBE())
+	c.Hash.EncodeBinary(w)
 }
 
 func (c *Conflicts) toJSONMap(m map[string]interface{}) {
diff --git a/pkg/core/transaction/not_valid_before.go b/pkg/core/transaction/not_valid_before.go
index 46868dc2b..232009f3d 100644
--- a/pkg/core/transaction/not_valid_before.go
+++ b/pkg/core/transaction/not_valid_before.go
@@ -1,9 +1,6 @@
 package transaction
 
 import (
-	"encoding/binary"
-	"fmt"
-
 	"github.com/nspcc-dev/neo-go/pkg/io"
 )
 
@@ -14,22 +11,12 @@ type NotValidBefore struct {
 
 // DecodeBinary implements the io.Serializable interface.
 func (n *NotValidBefore) DecodeBinary(br *io.BinReader) {
-	bytes := br.ReadVarBytes(4)
-	if br.Err != nil {
-		return
-	}
-	if len(bytes) != 4 {
-		br.Err = fmt.Errorf("expected 4 bytes, got %d", len(bytes))
-		return
-	}
-	n.Height = binary.LittleEndian.Uint32(bytes)
+	n.Height = br.ReadU32LE()
 }
 
 // EncodeBinary implements the io.Serializable interface.
 func (n *NotValidBefore) EncodeBinary(w *io.BinWriter) {
-	bytes := make([]byte, 4)
-	binary.LittleEndian.PutUint32(bytes, n.Height)
-	w.WriteVarBytes(bytes)
+	w.WriteU32LE(n.Height)
 }
 
 func (n *NotValidBefore) toJSONMap(m map[string]interface{}) {
diff --git a/pkg/core/transaction/notary_assisted.go b/pkg/core/transaction/notary_assisted.go
index 436c4f42c..5a7de29a4 100644
--- a/pkg/core/transaction/notary_assisted.go
+++ b/pkg/core/transaction/notary_assisted.go
@@ -1,8 +1,6 @@
 package transaction
 
 import (
-	"fmt"
-
 	"github.com/nspcc-dev/neo-go/pkg/io"
 )
 
@@ -13,20 +11,12 @@ type NotaryAssisted struct {
 
 // DecodeBinary implements the io.Serializable interface.
 func (n *NotaryAssisted) DecodeBinary(br *io.BinReader) {
-	bytes := br.ReadVarBytes(1)
-	if br.Err != nil {
-		return
-	}
-	if len(bytes) != 1 {
-		br.Err = fmt.Errorf("expected 1 byte, got %d", len(bytes))
-		return
-	}
-	n.NKeys = bytes[0]
+	n.NKeys = br.ReadB()
 }
 
 // EncodeBinary implements the io.Serializable interface.
 func (n *NotaryAssisted) EncodeBinary(w *io.BinWriter) {
-	w.WriteVarBytes([]byte{n.NKeys})
+	w.WriteB(n.NKeys)
 }
 
 func (n *NotaryAssisted) toJSONMap(m map[string]interface{}) {