diff --git a/field/composite.go b/field/composite.go
index d9a05e9b..5485c19e 100644
--- a/field/composite.go
+++ b/field/composite.go
@@ -6,12 +6,15 @@ import (
 	"fmt"
 	"reflect"
 	"regexp"
+	"strconv"
 
 	"github.com/moov-io/iso8583/padding"
 	"github.com/moov-io/iso8583/sort"
 	"github.com/moov-io/iso8583/utils"
 )
 
+const compositeBitmapKey = "0"
+
 var _ Field = (*Composite)(nil)
 var _ json.Marshaler = (*Composite)(nil)
 var _ json.Unmarshaler = (*Composite)(nil)
@@ -58,6 +61,8 @@ var _ json.Unmarshaler = (*Composite)(nil)
 type Composite struct {
 	spec *Spec
 
+	bitmap *Bitmap
+
 	orderedSpecFieldTags []string
 
 	// stores all fields according to the spec
@@ -115,7 +120,10 @@ func (f *Composite) SetSpec(spec *Spec) {
 		panic(err)
 	}
 	f.spec = spec
-	f.orderedSpecFieldTags = orderedKeys(spec.Subfields, spec.Tag.Sort)
+
+	if spec.Tag != nil && spec.Tag.Sort != nil {
+		f.orderedSpecFieldTags = orderedKeys(spec.Subfields, spec.Tag.Sort)
+	}
 }
 
 func (f *Composite) Unmarshal(v interface{}) error {
@@ -290,6 +298,18 @@ func (f *Composite) Bytes() ([]byte, error) {
 	return f.pack()
 }
 
+// Bitmap returns an instantiation of Bitmap using the BitmapSpec from the spec attribute.
+func (f *Composite) Bitmap() *Bitmap {
+	if f.bitmap == nil {
+		if field, ok := f.subfields[compositeBitmapKey]; ok {
+			f.bitmap = field.(*Bitmap)
+		}
+
+	}
+
+	return f.bitmap
+}
+
 // String iterates over the receiver's subfields, packs them and converts the
 // result to a string. The result does not incorporate the encoded aggregate
 // length of the subfields in the prefix.
@@ -342,6 +362,53 @@ func (f *Composite) UnmarshalJSON(b []byte) error {
 }
 
 func (f *Composite) pack() ([]byte, error) {
+	if f.Bitmap() != nil {
+		return f.packSubfieldsByBitmap()
+	}
+
+	return f.packSubfieldsByTag()
+}
+
+func (f *Composite) packSubfieldsByBitmap() ([]byte, error) {
+	packed := []byte{}
+	f.Bitmap().Reset()
+
+	ids, err := f.packableFieldIDs()
+	if err != nil {
+		return nil, fmt.Errorf("failed to pack message: %w", err)
+	}
+
+	for _, id := range ids {
+		// index 0 is for bitmap
+		// regular field number startd from index 1
+		idInt, err := strconv.Atoi(id)
+		if err != nil {
+			return nil, fmt.Errorf("failed to pack message: %w", err)
+		}
+
+		if idInt < 1 {
+			continue
+		}
+		f.Bitmap().Set(idInt)
+	}
+
+	// pack fields
+	for _, i := range ids {
+		field, ok := f.subfields[i]
+		if !ok {
+			return nil, fmt.Errorf("failed to pack field %v: no specification found", i)
+		}
+		packedField, err := field.Pack()
+		if err != nil {
+			return nil, fmt.Errorf("failed to pack field %v (%s): %w", i, field.Spec().Description, err)
+		}
+		packed = append(packed, packedField...)
+	}
+
+	return packed, nil
+}
+
+func (f *Composite) packSubfieldsByTag() ([]byte, error) {
 	packed := []byte{}
 	for _, tag := range f.orderedSpecFieldTags {
 		field, ok := f.subfields[tag]
@@ -377,6 +444,9 @@ func (f *Composite) pack() ([]byte, error) {
 }
 
 func (f *Composite) unpack(data []byte, isVariableLength bool) (int, error) {
+	if f.Bitmap() != nil {
+		return f.unpackSubfieldsByBitmap(data)
+	}
 	if f.spec.Tag.Enc != nil {
 		return f.unpackSubfieldsByTag(data)
 	}
@@ -442,21 +512,63 @@ func (f *Composite) unpackSubfieldsByTag(data []byte) (int, error) {
 	return offset, nil
 }
 
+func (f *Composite) unpackSubfieldsByBitmap(data []byte) (int, error) {
+	var off int
+
+	// reset fields that were set
+	f.setSubfields = map[string]struct{}{}
+
+	// unpack Bitmap
+	read, err := f.Bitmap().Unpack(data[off:])
+	if err != nil {
+		return 0, fmt.Errorf("failed to unpack bitmap: %w", err)
+	}
+
+	off += read
+
+	for i := 1; i <= f.Bitmap().Len(); i++ {
+		if f.Bitmap().IsSet(i) {
+			iStr := fmt.Sprintf("%v", i)
+
+			fl, ok := f.subfields[iStr]
+			if !ok {
+				return 0, fmt.Errorf("failed to unpack field %v: no specification found", iStr)
+			}
+
+			read, err = fl.Unpack(data[off:])
+			if err != nil {
+				return 0, fmt.Errorf("failed to unpack field %v (%s): %w", iStr, fl.Spec().Description, err)
+			}
+
+			f.setSubfields[iStr] = struct{}{}
+
+			off += read
+		}
+	}
+
+	return off, nil
+}
+
 func validateCompositeSpec(spec *Spec) error {
-	if spec.Tag == nil || spec.Tag.Sort == nil {
-		return fmt.Errorf("Composite spec requires a Tag.Sort function to be defined")
+	var bm *Bitmap
+	if value, ok := spec.Subfields[compositeBitmapKey]; ok {
+		bm = value.(*Bitmap)
 	}
-	if spec.Pad != nil && spec.Pad != padding.None {
-		return fmt.Errorf("Composite spec only supports nil or None spec padding values")
+
+	if (spec.Tag == nil || spec.Tag.Sort == nil) && bm == nil {
+		return fmt.Errorf("Composite spec requires a Tag.Sort function or a BitmapSpec to be defined")
 	}
-	if spec.Enc != nil {
-		return fmt.Errorf("Composite spec only supports a nil Enc value")
+	if spec.Tag != nil && spec.Tag.Sort != nil && bm != nil {
+		return fmt.Errorf("Composite spec doesn't support Tag.Sort function when a BitmapSpec is defined")
 	}
 	if spec.Tag != nil && spec.Tag.Enc == nil && spec.Tag.Length > 0 {
 		return fmt.Errorf("Composite spec requires a Tag.Enc to be defined if Tag.Length > 0")
 	}
-	if spec.Tag.Sort == nil {
-		return fmt.Errorf("Composite spec requires a Tag.Sort function to be defined")
+	if spec.Pad != nil && spec.Pad != padding.None {
+		return fmt.Errorf("Composite spec only supports nil or None spec padding values")
+	}
+	if spec.Enc != nil {
+		return fmt.Errorf("Composite spec only supports a nil Enc value")
 	}
 	return nil
 }
@@ -488,3 +600,21 @@ func getFieldIndexOrTag(field reflect.StructField) (string, error) {
 
 	return "", nil
 }
+
+func (f *Composite) packableFieldIDs() ([]string, error) {
+	// Index 0 represent bitmap which is always populated.
+	populatedFieldIDs := []string{compositeBitmapKey}
+
+	for id := range f.setSubfields {
+		// represents the bitmap
+		if id == compositeBitmapKey {
+			continue
+		}
+
+		populatedFieldIDs = append(populatedFieldIDs, id)
+	}
+
+	sort.StringsByInt(populatedFieldIDs)
+
+	return populatedFieldIDs, nil
+}
diff --git a/field/composite_test.go b/field/composite_test.go
index d2c9cba8..44e7076c 100644
--- a/field/composite_test.go
+++ b/field/composite_test.go
@@ -979,8 +979,8 @@ func TestCompositePanicsOnSpecValidationFailures(t *testing.T) {
 		spec *Spec
 	}{
 		{
-			desc: "panics on nil Tag being defined in spec",
-			err:  "Composite spec requires a Tag.Sort function to be defined",
+			desc: "panics on nil Tag and no Bitmap being defined in spec",
+			err:  "Composite spec requires a Tag.Sort function or a BitmapSpec to be defined",
 			spec: &Spec{
 				Length:    6,
 				Pref:      prefix.ASCII.Fixed,
@@ -989,8 +989,8 @@ func TestCompositePanicsOnSpecValidationFailures(t *testing.T) {
 			},
 		},
 		{
-			desc: "panics on nil Tag.Sort being defined in spec",
-			err:  "Composite spec requires a Tag.Sort function to be defined",
+			desc: "panics on nil Tag and no Bitmap being defined in spec",
+			err:  "Composite spec requires a Tag.Sort function or a BitmapSpec to be defined",
 			spec: &Spec{
 				Length:    6,
 				Pref:      prefix.ASCII.Fixed,