Index: Ringtoets/Piping/src/Ringtoets.Piping.Forms/Views/PipingFailureMechanismResultView.cs
===================================================================
diff -u -r74e362128e21e414c29a561f6e6fe113bcab2635 -r212b554dfd4ca66295fd34f33d9a49ba1fcc4e14
--- Ringtoets/Piping/src/Ringtoets.Piping.Forms/Views/PipingFailureMechanismResultView.cs	(.../PipingFailureMechanismResultView.cs)	(revision 74e362128e21e414c29a561f6e6fe113bcab2635)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Forms/Views/PipingFailureMechanismResultView.cs	(.../PipingFailureMechanismResultView.cs)	(revision 212b554dfd4ca66295fd34f33d9a49ba1fcc4e14)
@@ -103,8 +103,9 @@
         /// <returns><c>false</c> if the simple assessment has passed, <c>true</c> otherwise.</returns>
         private bool HasPassedSimpleAssessment(int rowIndex)
         {
-            return (SimpleAssessmentResultType) DataGridViewControl.GetCell(rowIndex, AssessmentLayerOneColumnIndex).Value
-                   == SimpleAssessmentResultType.ProbabilityNegligible;
+            var simpleAssessmentType = (SimpleAssessmentResultType) DataGridViewControl.GetCell(rowIndex, AssessmentLayerOneColumnIndex).Value;
+            return simpleAssessmentType == SimpleAssessmentResultType.ProbabilityNegligible
+                   || simpleAssessmentType == SimpleAssessmentResultType.NotApplicable;
         }
 
         protected override void Dispose(bool disposing)
@@ -180,7 +181,8 @@
 
             var resultRow = (PipingFailureMechanismSectionResultRow) GetDataAtRow(e.RowIndex);
             PipingFailureMechanismSectionResult rowObject = resultRow.GetSectionResult;
-            if (rowObject.SimpleAssessmentInput == SimpleAssessmentResultType.ProbabilityNegligible)
+            if (rowObject.SimpleAssessmentInput == SimpleAssessmentResultType.ProbabilityNegligible
+                || rowObject.SimpleAssessmentInput == SimpleAssessmentResultType.NotApplicable)
             {
                 currentDataGridViewCell.ErrorText = string.Empty;
                 return;
Index: Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/Views/PipingFailureMechanismResultViewTest.cs
===================================================================
diff -u -r74e362128e21e414c29a561f6e6fe113bcab2635 -r212b554dfd4ca66295fd34f33d9a49ba1fcc4e14
--- Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/Views/PipingFailureMechanismResultViewTest.cs	(.../PipingFailureMechanismResultViewTest.cs)	(revision 74e362128e21e414c29a561f6e6fe113bcab2635)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/Views/PipingFailureMechanismResultViewTest.cs	(.../PipingFailureMechanismResultViewTest.cs)	(revision 212b554dfd4ca66295fd34f33d9a49ba1fcc4e14)
@@ -191,7 +191,8 @@
                 Assert.AreEqual("-", cellAssessmentLayerTwoA.FormattedValue);
                 Assert.AreEqual("-", cellAssessmentLayerThree.FormattedValue);
 
-                if (simpleAssessmentType == SimpleAssessmentResultType.ProbabilityNegligible)
+                if (simpleAssessmentType == SimpleAssessmentResultType.ProbabilityNegligible
+                    || simpleAssessmentType == SimpleAssessmentResultType.NotApplicable)
                 {
                     DataGridViewTestHelper.AssertCellIsDisabled(cellAssessmentLayerTwoA);
                     DataGridViewTestHelper.AssertCellIsDisabled(cellAssessmentLayerThree);
@@ -275,7 +276,6 @@
 
         [Test]
         [TestCase(SimpleAssessmentResultType.None)]
-        [TestCase(SimpleAssessmentResultType.NotApplicable)]
         [TestCase(SimpleAssessmentResultType.AssessFurther)]
         public void FailureMechanismResultView_TotalContributionNotHundred_ShowsErrorTooltip(
             SimpleAssessmentResultType simpleAssessmentType)
@@ -309,7 +309,6 @@
         [Test]
         [SetCulture("nl-NL")]
         [TestCase(SimpleAssessmentResultType.None)]
-        [TestCase(SimpleAssessmentResultType.NotApplicable)]
         [TestCase(SimpleAssessmentResultType.AssessFurther)]
         public void FailureMechanismResultView_AssessmentLayerTwoAHasValue_DoesNotShowsErrorTooltip(
             SimpleAssessmentResultType simpleAssessmentType)
@@ -341,7 +340,6 @@
 
         [Test]
         [TestCase(SimpleAssessmentResultType.None)]
-        [TestCase(SimpleAssessmentResultType.NotApplicable)]
         [TestCase(SimpleAssessmentResultType.AssessFurther)]
         public void FailureMechanismResultView_AssessmentLayerTwoANull_ShowsErrorTooltip(SimpleAssessmentResultType simpleAssessmentType)
         {
@@ -372,7 +370,6 @@
 
         [Test]
         [TestCase(SimpleAssessmentResultType.None)]
-        [TestCase(SimpleAssessmentResultType.NotApplicable)]
         [TestCase(SimpleAssessmentResultType.AssessFurther)]
         public void FailureMechanismResultView_AssessmentLayerTwoANaN_ShowsErrorTooltip(SimpleAssessmentResultType simpleAssessmentType)
         {
@@ -404,7 +401,6 @@
 
         [Test]
         [TestCase(SimpleAssessmentResultType.None)]
-        [TestCase(SimpleAssessmentResultType.NotApplicable)]
         [TestCase(SimpleAssessmentResultType.AssessFurther)]
         public void FailureMechanismResultView_NoCalculationScenarios_ShowsErrorTooltip(SimpleAssessmentResultType simpleAssessmentType)
         {
@@ -431,7 +427,6 @@
 
         [Test]
         [TestCase(SimpleAssessmentResultType.None)]
-        [TestCase(SimpleAssessmentResultType.NotApplicable)]
         [TestCase(SimpleAssessmentResultType.AssessFurther)]
         public void FailureMechanismResultView_NoCalculationScenariosRelevant_ShowsErrorTooltip(
             SimpleAssessmentResultType simpleAssessmentType)