diff --git a/CHANGELOG.md b/CHANGELOG.md
index d93751342..a4d1c5c86 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,7 +12,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ### Added
 * Added support for mapping different EhrSupplyType (e.g. NHS prescription, OTC sale) into the Medication Statement Prescribing Agency extension
-* Added fallback for Condition.asserter to use the EHRComposition / author / agent field when EHRComposition / participant2 is absent
+* Added fallback for Condition.asserter to use the EHRComposition / author / agent field when EHRComposition / participant2 is absent.
+* 
+### Fixed
+* Improved error handling in SkeletonProcessingService to throw a meaningful IllegalArgumentException
+  when a payload node cannot be matched to a skeleton document ID, replacing an uninformative NullPointerException.
 
 ## [3.1.3] - 2025-09-19
 
diff --git a/gp2gp-translator/src/main/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingService.java b/gp2gp-translator/src/main/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingService.java
index 48d5582c6..7d26af0c5 100644
--- a/gp2gp-translator/src/main/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingService.java
+++ b/gp2gp-translator/src/main/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingService.java
@@ -79,6 +79,12 @@ private InboundMessage insertSkeletonIntoInboundMessagePayload(PatientAttachment
         var payloadXml = xPathService.parseDocumentFromXml(inboundMessage.getPayload());
         var valueNodes = xPathService.getNodes(payloadXml, "//*/@*[.='" + skeletonDocumentId + "']/parent::*/parent::*");
         var payloadNodeToReplace = valueNodes.item(0);
+
+        if (payloadNodeToReplace == null) {
+            throw new IllegalArgumentException(
+                    "Could not find payload node matching skeleton document ID: " + skeletonDocumentId
+            );
+        }
         var payloadNodeToReplaceParent = payloadNodeToReplace.getParentNode();
 
         var skeletonExtractNodes = skeletonExtractDocument.getElementsByTagName("*");
diff --git a/gp2gp-translator/src/test/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingServiceTests.java b/gp2gp-translator/src/test/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingServiceTests.java
index bfc2df0bc..186126ba9 100644
--- a/gp2gp-translator/src/test/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingServiceTests.java
+++ b/gp2gp-translator/src/test/java/uk/nhs/adaptors/pss/translator/service/SkeletonProcessingServiceTests.java
@@ -210,6 +210,30 @@ void When_SkeletonAsSectionMessageAndEBXMLSkeletonReferenceIsEmpty_Expect_Illega
                 inboundMessage, migrationRequest.getConversationId()));
     }
 
+    @Test
+    void When_SkeletonAsSectionMessageAndPayloadNodeNotFound_Expect_IllegalArgumentException()
+            throws SAXException {
+        var inboundMessage = new InboundMessage();
+        var attachmentLog = createSkeletonPatientAttachmentLog();
+
+        inboundMessage.setPayload(readInboundMessagePayloadFromFile());
+        inboundMessage.setEbXML(readInboundMessageEbXmlFromFile());
+
+        var reference = new EbxmlReference("First instance is always a payload", "mid:1", "docId");
+        var ebXmlAttachments = List.of(reference);
+        var fileAsBytes = readInboundMessageSkeletonPayloadFromFile().getBytes(StandardCharsets.UTF_8);
+
+        when(attachmentHandlerService.getAttachment(any(), any())).thenReturn(fileAsBytes);
+        when(xmlParseUtilService.getEbxmlAttachmentsData(any())).thenReturn(ebXmlAttachments);
+        when(xPathService.parseDocumentFromXml(any())).thenReturn(ebXmlDocument);
+        when(xPathService.getNodes(any(), any())).thenReturn(nodeList);
+        when(nodeList.item(0)).thenReturn(null);
+
+        assertThrows(IllegalArgumentException.class, () ->
+                skeletonProcessingService.updateInboundMessageWithSkeleton(attachmentLog,
+                        inboundMessage, migrationRequest.getConversationId()));
+    }
+
     PatientAttachmentLog createSkeletonPatientAttachmentLog() {
         return
             PatientAttachmentLog.builder()