diff --git a/parser/save.go b/parser/save.go
index db0535c..8511211 100644
--- a/parser/save.go
+++ b/parser/save.go
@@ -57,11 +57,37 @@ func Save(doc *Document, composableDocs []*Document, output string, outFormat st
 func AppendComposableDocument(res *Document, cdoc *Document, w io.Writer, outFormat string) {
 
 	res.SPDXDocRef.Annotations = append(res.SPDXDocRef.Annotations, cdoc.SPDXDocRef.Annotations...)
-	res.SPDXDocRef.ExternalDocumentReferences = append(res.SPDXDocRef.ExternalDocumentReferences, cdoc.SPDXDocRef.ExternalDocumentReferences...)
-	res.SPDXDocRef.Files = append(res.SPDXDocRef.Files, cdoc.SPDXDocRef.Files...)
-	res.SPDXDocRef.OtherLicenses = append(res.SPDXDocRef.OtherLicenses, cdoc.SPDXDocRef.OtherLicenses...)
-	res.SPDXDocRef.Packages = append(res.SPDXDocRef.Packages, cdoc.SPDXDocRef.Packages...)
-	res.SPDXDocRef.Relationships = append(res.SPDXDocRef.Relationships, cdoc.SPDXDocRef.Relationships...)
+
+	for _, e := range cdoc.SPDXDocRef.ExternalDocumentReferences {
+		if isNotDuplicate(e.Checksum.Value, res, EDR) {
+			res.SPDXDocRef.ExternalDocumentReferences = append(res.SPDXDocRef.ExternalDocumentReferences, e)
+		}
+	}
+	for _, f := range cdoc.SPDXDocRef.Files {
+		if areNotIdenticalChecksums(f.Checksums, res, FL) {
+			res.SPDXDocRef.Files = append(res.SPDXDocRef.Files, f)
+		}
+	}
+	for _, ol := range cdoc.SPDXDocRef.OtherLicenses {
+		if isNotDuplicate(ol.LicenseIdentifier, res, OL) {
+			res.SPDXDocRef.OtherLicenses = append(res.SPDXDocRef.OtherLicenses, ol)
+		}
+	}
+	for _, p := range cdoc.SPDXDocRef.Packages {
+		if areNotIdenticalChecksums(p.PackageChecksums, res, PKG) {
+			res.SPDXDocRef.Packages = append(res.SPDXDocRef.Packages, p)
+		}
+	}
+	for _, r := range cdoc.SPDXDocRef.Relationships {
+		relStr := fmt.Sprintf("%s_%s_%s_%s_%s_%s_%s_%s",
+			r.RefA.DocumentRefID, r.RefA.ElementRefID, r.RefA.SpecialID,
+			r.Relationship,
+			r.RefB.DocumentRefID, r.RefB.ElementRefID, r.RefB.SpecialID,
+			r.RelationshipComment)
+		if isNotDuplicate(relStr, res, RL) {
+			res.SPDXDocRef.Relationships = append(res.SPDXDocRef.Relationships, r)
+		}
+	}
 	res.SPDXDocRef.Reviews = append(res.SPDXDocRef.Reviews, cdoc.SPDXDocRef.Reviews...)
 	res.SPDXDocRef.Snippets = append(res.SPDXDocRef.Snippets, cdoc.SPDXDocRef.Snippets...)
 }
diff --git a/parser/spdx_utils.go b/parser/spdx_utils.go
new file mode 100644
index 0000000..3ee3785
--- /dev/null
+++ b/parser/spdx_utils.go
@@ -0,0 +1,75 @@
+// Copyright (c) 2022 VMware, Inc. All Rights Reserved.
+// SPDX-License-Identifier: BSD-2-Clause
+
+package parser
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/spdx/tools-golang/spdx"
+)
+
+const (
+	EDR string = "external_document_reference"
+	FL         = "file"
+	OL         = "other_license"
+	PKG        = "package"
+	RL         = "relationship"
+)
+
+func areNotIdenticalChecksums(checksums []spdx.Checksum, doc *Document, t string) bool {
+
+	switch t {
+	case "file":
+		for _, f := range doc.SPDXDocRef.Files {
+			if len(checksums) > 0 && reflect.DeepEqual(checksums, f.Checksums) {
+				return false
+			}
+		}
+
+	case "package":
+		for _, p := range doc.SPDXDocRef.Packages {
+			if len(checksums) > 0 && reflect.DeepEqual(checksums, p.PackageChecksums) {
+				return false
+			}
+		}
+	default:
+		return true
+	}
+	return true
+}
+
+func isNotDuplicate(data string, doc *Document, t string) bool {
+	switch t {
+	case "external_document_reference":
+		for _, edr := range doc.SPDXDocRef.ExternalDocumentReferences {
+			if len(data) > 0 && edr.Checksum.Value == data {
+				return false
+			}
+		}
+
+	case "other_license":
+		for _, ol := range doc.SPDXDocRef.OtherLicenses {
+			if len(data) > 0 && ol.LicenseIdentifier == data {
+				return false
+			}
+		}
+
+	case "relationship":
+		for _, r := range doc.SPDXDocRef.Relationships {
+			relStr := fmt.Sprintf("%s_%s_%s_%s_%s_%s_%s_%s",
+				r.RefA.DocumentRefID, r.RefA.ElementRefID, r.RefA.SpecialID,
+				r.Relationship,
+				r.RefB.DocumentRefID, r.RefB.ElementRefID, r.RefB.SpecialID,
+				r.RelationshipComment)
+			if len(data) > 0 && relStr == data {
+				return false
+			}
+		}
+
+	default:
+		return true
+	}
+	return true
+}