diff --git a/ifrs17/Constants/Validations.ipynb b/ifrs17/Constants/Validations.ipynb
index 64a58f8c..5f22aca2 100644
--- a/ifrs17/Constants/Validations.ipynb
+++ b/ifrs17/Constants/Validations.ipynb
@@ -78,7 +78,7 @@
                 "\n    // Data Note State",
                 "\n    ChangeDataNodeState, InactiveDataNodeState,",
                 "\n    // Parameters",
-                "\n    ReinsuranceCoverageDataNode, DuplicateInterDataNode, DuplicateSingleDataNode, InvalidDataNode, ",
+                "\n    ReinsuranceCoverageDataNode, DuplicateInterDataNode, DuplicateSingleDataNode, InvalidDataNode, InvalidDataNodeForOpening,",
                 "\n    // Storage",
                 "\n    DataNodeNotFound, PartnerNotFound, RatingNotFound, CreditDefaultRateNotFound, MissingPremiumAllocation, ReinsuranceCoverage, ",
                 "\n    YieldCurveNotFound, YieldCurvePeriodNotApplicable, EconomicBasisNotFound, AccountingVariableTypeNotFound,",
@@ -150,6 +150,7 @@
                 "\n    (Error.DuplicateInterDataNode         , 2) => $\"Duplicated Inter-DataNode parameter for {s[0]}-{s[1]} is found.\",",
                 "\n    (Error.DuplicateSingleDataNode        , 1) => $\"Duplicated Single-DataNode parameter for {s[0]} is found.\",",
                 "\n    (Error.InvalidDataNode                , 1) => $\"Data imported for invalid Data Node {s[0]}.\",",
+                "\n    (Error.InvalidDataNodeForOpening      , 1) => $\"Data imported for invalid Data Node or for a Data Node after its inception year {s[0]}.\",",
                 "\n    // Storage",
                 "\n    (Error.DataNodeNotFound               , 1) => $\"DataNode {s[0]} not found.\",",
                 "\n    (Error.PartnerNotFound                , 1) => $\"Partner not found for DataNode {s[0]}.\",",
diff --git a/ifrs17/Import/Importers.ipynb b/ifrs17/Import/Importers.ipynb
index f4737847..52c5a764 100644
--- a/ifrs17/Import/Importers.ipynb
+++ b/ifrs17/Import/Importers.ipynb
@@ -209,9 +209,14 @@
                 "\n        return aoc;",
                 "\n    }",
                 "\n    ",
-                "\n    public string ValidateDataNode(string goc) {",
+                "\n    public string ValidateDataNode(string goc, string importFormat) {",
                 "\n        if (!DataNodeDataBySystemName.ContainsKey(goc))",
-                "\n            ApplicationMessage.Log(Error.InvalidDataNode, goc);",
+                "\n        {",
+                "\n            if( importFormat == ImportFormats.Opening )",
+                "\n                ApplicationMessage.Log(Error.InvalidDataNodeForOpening, goc);",
+                "\n            else",
+                "\n                ApplicationMessage.Log(Error.InvalidDataNode, goc);",
+                "\n        }",
                 "\n        return goc;",
                 "\n    }",
                 "\n    ",
@@ -1133,7 +1138,7 @@
                 "\n                                ? accidentYear",
                 "\n                                : (int?)null,",
                 "\n                Partition = parsingStorage.TargetPartitionByReportingNodeAndPeriod.Id,",
-                "\n                Values = Multiply(GetSign((aocType, valueType.AmountType, valueType.EstimateType, dataNodeData.IsReinsurance), parsingStorage.HierarchyCache), values)",
+                "\n                Values = Multiply(GetSign((ImportFormats.Cashflow, aocType, valueType.AmountType, valueType.EstimateType, dataNodeData.IsReinsurance), parsingStorage.HierarchyCache), values)",
                 "\n            };",
                 "\n            return item;",
                 "\n        }, ImportFormats.Cashflow",
@@ -1234,7 +1239,7 @@
                 "\n                AmountType = valueType.AmountType,",
                 "\n                EstimateType = valueType.EstimateType,",
                 "\n                Partition = parsingStorage.TargetPartitionByReportingNodeAndPeriod.Id,",
-                "\n                Value = GetSign((aocType, valueType.AmountType, valueType.EstimateType, dataNodeData.IsReinsurance), parsingStorage.HierarchyCache) * datarow.Field<string>(nameof(IfrsVariable.Value)).CheckStringForExponentialAndConvertToDouble()",
+                "\n                Value = GetSign((ImportFormats.Actual, aocType, valueType.AmountType, valueType.EstimateType, dataNodeData.IsReinsurance), parsingStorage.HierarchyCache) * datarow.Field<string>(nameof(IfrsVariable.Value)).CheckStringForExponentialAndConvertToDouble()",
                 "\n            };",
                 "\n            return item;",
                 "\n        }, ImportFormats.Actual",
@@ -1308,7 +1313,7 @@
                 "\n",
                 "\n    var importLog = await Import.FromDataSet(dataSet)",
                 "\n        .WithType<IfrsVariable> ( (dataset, datarow) => {",
-                "\n            var dataNode = parsingStorage.ValidateDataNode(datarow.Field<string>(nameof(DataNode)));",
+                "\n            var dataNode = parsingStorage.ValidateDataNode(datarow.Field<string>(nameof(DataNode)),importFormat);",
                 "\n            var amountType = parsingStorage.ValidateAmountType(datarow.Field<string>(nameof(IfrsVariable.AmountType)));",
                 "\n            var estimateType = parsingStorage.ValidateEstimateType(datarow.Field<string>(nameof(IfrsVariable.EstimateType)), dataNode); //TODO LIC/LRC dependence",
                 "\n            var aocStep = importFormat == ImportFormats.SimpleValue ",
@@ -1330,7 +1335,7 @@
                 "\n                EstimateType = estimateType,",
                 "\n                EconomicBasis = economicBasis,",
                 "\n                Partition = parsingStorage.TargetPartitionByReportingNodeAndPeriod.Id,",
-                "\n                Value = GetSign((aocStep.AocType, amountType, estimateType, parsingStorage.IsDataNodeReinsurance(dataNode)), parsingStorage.HierarchyCache) * datarow.Field<string>(nameof(IfrsVariable.Value)).CheckStringForExponentialAndConvertToDouble()",
+                "\n                Value = GetSign((importFormat, aocStep.AocType, amountType, estimateType, parsingStorage.IsDataNodeReinsurance(dataNode)), parsingStorage.HierarchyCache) * datarow.Field<string>(nameof(IfrsVariable.Value)).CheckStringForExponentialAndConvertToDouble()",
                 "\n            };",
                 "\n            return iv;",
                 "\n        }, importFormat // This should indicate the table name, not the input format",
diff --git a/ifrs17/Utils/ImportCalculationMethods.ipynb b/ifrs17/Utils/ImportCalculationMethods.ipynb
index 1c394e71..a380baa8 100644
--- a/ifrs17/Utils/ImportCalculationMethods.ipynb
+++ b/ifrs17/Utils/ImportCalculationMethods.ipynb
@@ -219,7 +219,7 @@
         {
             "cell_type": "code",
             "source": [
-                "public static int GetSign((string AocType, string AmountType, string EstimateType, bool IsReinsurance) variable, Systemorph.Vertex.Hierarchies.IHierarchicalDimensionCache hierarchyCache) => 1;"
+                "public static int GetSign((string importFormat, string AocType, string AmountType, string EstimateType, bool IsReinsurance) variable, Systemorph.Vertex.Hierarchies.IHierarchicalDimensionCache hierarchyCache) => 1;"
             ],
             "metadata": {},
             "execution_count": 0,