diff --git a/src/main/java/de/gecheckt/asv/validation/structure/DefaultStructureValidator.java b/src/main/java/de/gecheckt/asv/validation/structure/DefaultStructureValidator.java
index 5f15360..7863b94 100644
--- a/src/main/java/de/gecheckt/asv/validation/structure/DefaultStructureValidator.java
+++ b/src/main/java/de/gecheckt/asv/validation/structure/DefaultStructureValidator.java
@@ -26,6 +26,7 @@ import de.gecheckt.asv.validation.model.ValidationSeverity;
  * 8. Die im UNT angegebene Segmentanzahl muss der tatsächlichen Anzahl der Segmente entsprechen
  * 9. Eine Nachricht muss mindestens ein UNH-Segment enthalten
  * 10. Eine Nachricht muss mindestens ein UNT-Segment enthalten
+ * 11. UNH muss vor UNT stehen
  */
 public class DefaultStructureValidator implements StructureValidator {
     
@@ -111,6 +112,12 @@ public class DefaultStructureValidator implements StructureValidator {
             if (message.getFirstSegment("UNT").isPresent()) {
                 validateUntSegmentCount(message, errors);
             }
+            
+            // Regel 11: UNH muss vor UNT stehen
+            // Nur prüfen, wenn beide Segmente vorhanden sind
+            if (message.getFirstSegment("UNH").isPresent() && message.getFirstSegment("UNT").isPresent()) {
+                validateUnhBeforeUnt(message, errors);
+            }
         }
     }
     
@@ -207,6 +214,38 @@ public class DefaultStructureValidator implements StructureValidator {
         }
     }
     
+    /**
+     * Validiert, dass UNH vor UNT steht.
+     * 
+     * @param message die zu validierende Nachricht
+     * @param errors die Liste zum Hinzufügen von Validierungsfehlern
+     */
+    private void validateUnhBeforeUnt(Message message, List<ValidationError> errors) {
+        var unhSegment = message.getFirstSegment("UNH");
+        var untSegment = message.getFirstSegment("UNT");
+        
+        // Prüft, ob beide Segmente vorhanden sind, bevor eine Validierung erfolgt
+        if (unhSegment.isPresent() && untSegment.isPresent()) {
+            int unhPosition = unhSegment.get().segmentPosition();
+            int untPosition = untSegment.get().segmentPosition();
+            
+            // UNH muss vor UNT stehen
+            if (unhPosition > untPosition) {
+                errors.add(createError(
+                    "STRUCTURE_011",
+                    "UNH muss vor UNT stehen",
+                    ValidationSeverity.ERROR,
+                    "UNH/UNT",
+                    message.messagePosition(),
+                    "",
+                    0,
+                    "UNH at position " + unhPosition + ", UNT at position " + untPosition,
+                    "UNH muss vor UNT stehen"
+                ));
+            }
+        }
+    }
+    
     /**
      * Validiert, dass die Referenznummern in UNH und UNT übereinstimmen.
      * 
diff --git a/src/test/java/de/gecheckt/asv/validation/structure/DefaultStructureValidatorTest.java b/src/test/java/de/gecheckt/asv/validation/structure/DefaultStructureValidatorTest.java
index 1944438..9f5780f 100644
--- a/src/test/java/de/gecheckt/asv/validation/structure/DefaultStructureValidatorTest.java
+++ b/src/test/java/de/gecheckt/asv/validation/structure/DefaultStructureValidatorTest.java
@@ -438,4 +438,87 @@ class DefaultStructureValidatorTest {
         assertFalse(result.getErrors().stream()
             .anyMatch(error -> "STRUCTURE_008".equals(error.errorCode())));
     }
+    
+    @Test
+    void validate_shouldReportErrorWhenUnhComesAfterUnt() throws IOException, InputFileParseException {
+        // Given
+        SegmentLineTokenizer tokenizer = new DefaultSegmentLineTokenizer();
+        DefaultInputFileParser parser = new DefaultInputFileParser(tokenizer);
+        String fileName = "unt-before-unh-invalid.asv";
+        Path filePath = Path.of("src/test/resources/unt-before-unh-invalid.asv");
+        String fileContent = Files.readString(filePath);
+        
+        // When
+        InputFile inputFile = parser.parse(fileName, fileContent);
+        ValidationResult result = validator.validate(inputFile);
+        
+        // Then
+        assertTrue(result.hasErrors());
+        assertEquals(1, result.getErrors().size());
+        
+        ValidationError error = result.getErrors().get(0);
+        assertEquals("STRUCTURE_011", error.errorCode());
+        assertEquals("UNH muss vor UNT stehen", error.description());
+        assertEquals("UNH/UNT", error.segmentName());
+        assertEquals(1, error.segmentPosition());
+        assertEquals("UNH at position 9, UNT at position 1", error.actualValue());
+        assertEquals("UNH muss vor UNT stehen", error.expectedRule());
+    }
+    
+    @Test
+    void validate_shouldNotReportErrorWhenUnhComesBeforeUnt() throws IOException, InputFileParseException {
+        // Given
+        SegmentLineTokenizer tokenizer = new DefaultSegmentLineTokenizer();
+        DefaultInputFileParser parser = new DefaultInputFileParser(tokenizer);
+        String fileName = "unh-before-unt-valid.asv";
+        Path filePath = Path.of("src/test/resources/unh-before-unt-valid.asv");
+        String fileContent = Files.readString(filePath);
+        
+        // When
+        InputFile inputFile = parser.parse(fileName, fileContent);
+        ValidationResult result = validator.validate(inputFile);
+        
+        // Then
+        // Should not have STRUCTURE_011 error for UNH/UNT order
+        assertFalse(result.getErrors().stream()
+            .anyMatch(error -> "STRUCTURE_011".equals(error.errorCode())));
+    }
+    
+    @Test
+    void validate_shouldNotReportErrorWhenUnhIsMissing() throws IOException, InputFileParseException {
+        // Given
+        SegmentLineTokenizer tokenizer = new DefaultSegmentLineTokenizer();
+        DefaultInputFileParser parser = new DefaultInputFileParser(tokenizer);
+        String fileName = "no-unh.asv";
+        Path filePath = Path.of("src/test/resources/no-unh.asv");
+        String fileContent = Files.readString(filePath);
+        
+        // When
+        InputFile inputFile = parser.parse(fileName, fileContent);
+        ValidationResult result = validator.validate(inputFile);
+        
+        // Then
+        // Should not have STRUCTURE_011 error for UNH/UNT order when UNH is missing
+        assertFalse(result.getErrors().stream()
+            .anyMatch(error -> "STRUCTURE_011".equals(error.errorCode())));
+    }
+    
+    @Test
+    void validate_shouldNotReportErrorWhenUntIsMissing() throws IOException, InputFileParseException {
+        // Given
+        SegmentLineTokenizer tokenizer = new DefaultSegmentLineTokenizer();
+        DefaultInputFileParser parser = new DefaultInputFileParser(tokenizer);
+        String fileName = "no-unt.asv";
+        Path filePath = Path.of("src/test/resources/no-unt.asv");
+        String fileContent = Files.readString(filePath);
+        
+        // When
+        InputFile inputFile = parser.parse(fileName, fileContent);
+        ValidationResult result = validator.validate(inputFile);
+        
+        // Then
+        // Should not have STRUCTURE_011 error for UNH/UNT order when UNT is missing
+        assertFalse(result.getErrors().stream()
+            .anyMatch(error -> "STRUCTURE_011".equals(error.errorCode())));
+    }
 }
\ No newline at end of file
diff --git a/src/test/resources/unh-before-unt-valid.asv b/src/test/resources/unh-before-unt-valid.asv
new file mode 100644
index 0000000..c5da9ec
--- /dev/null
+++ b/src/test/resources/unh-before-unt-valid.asv
@@ -0,0 +1,9 @@
+UNH+1+ORDERS:D:03B:UN:EAN008'
+BGM+220+100001'
+DTM+137:20260325:102'
+NAD+BY+5000000000000:16++Customer Name'
+LIN+1++Product123:SA'
+QTY+21:10:PCE'
+UNS+S'
+CNT+2:1'
+UNT+8+1'
\ No newline at end of file
diff --git a/src/test/resources/unt-before-unh-invalid.asv b/src/test/resources/unt-before-unh-invalid.asv
new file mode 100644
index 0000000..e4402c8
--- /dev/null
+++ b/src/test/resources/unt-before-unh-invalid.asv
@@ -0,0 +1,9 @@
+UNT+9+1'
+BGM+220+100001'
+DTM+137:20260325:102'
+NAD+BY+5000000000000:16++Customer Name'
+LIN+1++Product123:SA'
+QTY+21:10:PCE'
+UNS+S'
+CNT+2:1'
+UNH+1+ORDERS:D:03B:UN:EAN008'
\ No newline at end of file