diff --git a/application/CohortManager/src/Functions/ScreeningValidationService/StaticValidation/Breast_Screening_staticRules.json b/application/CohortManager/src/Functions/ScreeningValidationService/StaticValidation/Breast_Screening_staticRules.json
index 53d5dc91ab..7e888160ec 100644
--- a/application/CohortManager/src/Functions/ScreeningValidationService/StaticValidation/Breast_Screening_staticRules.json
+++ b/application/CohortManager/src/Functions/ScreeningValidationService/StaticValidation/Breast_Screening_staticRules.json
@@ -97,7 +97,7 @@
     "Rules": [
       {
         "RuleName": "30.Postcode.NBO.NonFatal",
-        "Expression": "string.IsNullOrEmpty(participant.Postcode) OR ValidationHelper.ValidatePostcode(participant.Postcode)",
+        "Expression": "string.IsNullOrEmpty(participant.Postcode) OR ValidationHelper.ValidatePostcode(participant.Postcode) OR participant.Postcode == \"ZZZSECUR\"",
         "Actions": {
           "OnFailure": {
             "Name": "OutputExpression",
diff --git a/application/CohortManager/src/Functions/Shared/Common/ValidationHelper.cs b/application/CohortManager/src/Functions/Shared/Common/ValidationHelper.cs
index 131de111ba..9c71573343 100644
--- a/application/CohortManager/src/Functions/Shared/Common/ValidationHelper.cs
+++ b/application/CohortManager/src/Functions/Shared/Common/ValidationHelper.cs
@@ -88,14 +88,12 @@ public static bool ValidateNHSNumber(string nhsNumber)
     public static bool ValidatePostcode(string postcode)
     {
         string validPostcodePattern = "^([A-Za-z][A-Ha-hJ-Yj-y]?[0-9][A-Za-z0-9]? ?[0-9][A-Za-z]{2}|[Gg][Ii][Rr] ?0[Aa]{2})$";
-        string dummyPostcodePattern1 = "^ZZ99 ?[0-9][A-Z]{2}$";
-        string dummyPostcodePattern2 = "^ZZZSECUR$";
+        string dummyPostcodePattern = "^ZZ99 ?[0-9][A-Z]{2}$";
 
         Match validPostcodeMatch = Regex.Match(postcode, validPostcodePattern, RegexOptions.IgnoreCase, TimeSpan.FromSeconds(2));
-        Match dummyPostcodeMatch1 = Regex.Match(postcode, dummyPostcodePattern1, RegexOptions.IgnoreCase, TimeSpan.FromSeconds(2));
-        Match dummyPostcodeMatch2 = Regex.Match(postcode, dummyPostcodePattern2, RegexOptions.IgnoreCase, TimeSpan.FromSeconds(2));
+        Match dummyPostcodeMatch = Regex.Match(postcode, dummyPostcodePattern, RegexOptions.IgnoreCase, TimeSpan.FromSeconds(2));
 
-        if (validPostcodeMatch.Success || dummyPostcodeMatch1.Success || dummyPostcodeMatch2.Success)
+        if (validPostcodeMatch.Success || dummyPostcodeMatch.Success)
             return true;
 
         return false;
diff --git a/tests/UnitTests/ScreeningValidationServiceTests/StaticValidation/StaticValidationTests.cs b/tests/UnitTests/ScreeningValidationServiceTests/StaticValidation/StaticValidationTests.cs
index 95c022b6df..d05c072da8 100644
--- a/tests/UnitTests/ScreeningValidationServiceTests/StaticValidation/StaticValidationTests.cs
+++ b/tests/UnitTests/ScreeningValidationServiceTests/StaticValidation/StaticValidationTests.cs
@@ -210,6 +210,7 @@ public async Task Run_DelRecord_DoNotRunCommonRules()
     [DataRow("ZZ99 9FZ")]
     [DataRow("ZZ999FZ")]
     [DataRow("ZZ99 3WZ")]
+    [DataRow("ZZZSECUR")]
     public async Task Run_ValidPostcode_ReturnNoContent(string postcode)
     {
         // Arrange
diff --git a/tests/UnitTests/StaticTests/ValidationHelperTests.cs b/tests/UnitTests/StaticTests/ValidationHelperTests.cs
index bf8ccb33db..878c0160cc 100644
--- a/tests/UnitTests/StaticTests/ValidationHelperTests.cs
+++ b/tests/UnitTests/StaticTests/ValidationHelperTests.cs
@@ -73,4 +73,29 @@ public void ValidatePastDate_InvalidPastDateAlwaysFuture_ReturnsFalse()
 
         Assert.IsFalse(result);
     }
+
+    [TestMethod]
+    [DataRow("B33 8TH")]                 // Valid postcode format
+    [DataRow("SW1A 1AA")]                // Valid postcode format
+    [DataRow("SM1 1AA")]                 // Valid postcode format
+    [DataRow("ZZ99 3CZ")]                // dummy postcode format
+    public void ValidatePostcode_ValidPostcode_ReturnsTrue(string postCode)
+    {
+        var result = ValidationHelper.ValidatePostcode(postCode);
+
+        Assert.IsTrue(result);
+    }
+
+    [TestMethod]
+    [DataRow("A1")]
+    [DataRow("ABCDE 123")]
+    [DataRow("123 ABC")]
+    [DataRow("W1A")]
+    [DataRow("SW1A1AAA")]
+    public void ValidatePostcode_InvalidPostcode_ReturnsFalse(string postCode)
+    {
+        var result = ValidationHelper.ValidatePostcode(postCode);
+
+        Assert.IsFalse(result);
+    }
 }