diff --git a/ClosedXML/Excel/Cells/XLCell.cs b/ClosedXML/Excel/Cells/XLCell.cs
index d667470..151e47b 100644
--- a/ClosedXML/Excel/Cells/XLCell.cs
+++ b/ClosedXML/Excel/Cells/XLCell.cs
@@ -1478,7 +1478,6 @@
 
         private IXLStyle GetStyle()
         {
-            //return _style ?? (_style = new XLStyle(this, Worksheet.Workbook.GetStyleById(_styleCacheId)));
             if (_style != null)
                 return _style;
 
diff --git a/ClosedXML/Excel/PivotTables/PivotValues/IXLPivotValueFormat.cs b/ClosedXML/Excel/PivotTables/PivotValues/IXLPivotValueFormat.cs
index 6ccaedf..c0988d5 100644
--- a/ClosedXML/Excel/PivotTables/PivotValues/IXLPivotValueFormat.cs
+++ b/ClosedXML/Excel/PivotTables/PivotValues/IXLPivotValueFormat.cs
@@ -1,13 +1,11 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 
 namespace ClosedXML.Excel
 {
-    public interface IXLPivotValueFormat: IXLNumberFormatBase
+    public interface IXLPivotValueFormat : IXLNumberFormatBase
     {
         IXLPivotValue SetNumberFormatId(Int32 value);
+
         IXLPivotValue SetFormat(String value);
     }
 }
diff --git a/ClosedXML/Excel/PivotTables/PivotValues/XLPivotValue.cs b/ClosedXML/Excel/PivotTables/PivotValues/XLPivotValue.cs
index e3ef842..50753cb 100644
--- a/ClosedXML/Excel/PivotTables/PivotValues/XLPivotValue.cs
+++ b/ClosedXML/Excel/PivotTables/PivotValues/XLPivotValue.cs
@@ -14,7 +14,7 @@
         }
 
         public IXLPivotValueFormat NumberFormat { get; private set; }
-        public String SourceName { get; private set; }	
+        public String SourceName { get; private set; }
         public String CustomName { get; set; }		public IXLPivotValue SetCustomName(String value) { CustomName = value; return this; }
 
         public XLPivotSummary SummaryFormula { get; set; }		public IXLPivotValue SetSummaryFormula(XLPivotSummary value) { SummaryFormula = value; return this; }
diff --git a/ClosedXML/Excel/Style/IXLNumberFormat.cs b/ClosedXML/Excel/Style/IXLNumberFormat.cs
index 1490413..ac12786 100644
--- a/ClosedXML/Excel/Style/IXLNumberFormat.cs
+++ b/ClosedXML/Excel/Style/IXLNumberFormat.cs
@@ -2,9 +2,10 @@
 
 namespace ClosedXML.Excel
 {
-    public interface IXLNumberFormat: IXLNumberFormatBase, IEquatable<IXLNumberFormat>
+    public interface IXLNumberFormat : IXLNumberFormatBase, IEquatable<IXLNumberFormat>
     {
         IXLStyle SetNumberFormatId(Int32 value);
+
         IXLStyle SetFormat(String value);
     }
 }
diff --git a/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs b/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs
index 0f1c4ca..8c5b0ce 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs
@@ -133,7 +133,7 @@
         internal struct NumberFormatInfo
         {
             public Int32 NumberFormatId;
-            public IXLNumberFormat NumberFormat;
+            public IXLNumberFormatBase NumberFormat;
         }
         #endregion
         #region Nested type: StyleInfo
@@ -148,8 +148,8 @@
         }
         #endregion
 
-        
-        
-       
+
+
+
     }
-}
\ No newline at end of file
+}
diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index e6924a3..791b00c 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -2522,7 +2522,7 @@
             var sharedBorders = new Dictionary<IXLBorder, BorderInfo>
             {{defaultStyle.Border, new BorderInfo {BorderId = 0, Border = defaultStyle.Border as XLBorder}}};
 
-            var sharedNumberFormats = new Dictionary<IXLNumberFormat, NumberFormatInfo>
+            var sharedNumberFormats = new Dictionary<IXLNumberFormatBase, NumberFormatInfo>
             {
                 {
                     defaultStyle.NumberFormat,
@@ -2573,6 +2573,7 @@
             UInt32 borderCount = 1;
             var numberFormatCount = 1;
             var xlStyles = new HashSet<Int32>();
+            var pivotTableNumberFormats = new HashSet<IXLPivotValueFormat>();
 
             foreach (var worksheet in WorksheetsInternal)
             {
@@ -2591,6 +2592,24 @@
                             s => !xlStyles.Contains(s))
                     )
                     xlStyles.Add(s);
+
+                foreach (var ptnf in worksheet.PivotTables.SelectMany(pt => pt.Values.Select(ptv => ptv.NumberFormat)).Distinct().Where(nf => !pivotTableNumberFormats.Contains(nf)))
+                    pivotTableNumberFormats.Add(ptnf);
+            }
+
+            foreach (var numberFormat in pivotTableNumberFormats)
+            {
+                if (numberFormat.NumberFormatId != -1
+                    || sharedNumberFormats.ContainsKey(numberFormat))
+                    continue;
+
+                sharedNumberFormats.Add(numberFormat,
+                    new NumberFormatInfo
+                    {
+                        NumberFormatId = numberFormatCount + 164,
+                        NumberFormat = numberFormat
+                    });
+                numberFormatCount++;
             }
 
             foreach (var xlStyle in xlStyles.Select(GetStyleById))
@@ -3317,9 +3336,9 @@
             return nf.Equals(xlFont);
         }
 
-        private static Dictionary<IXLNumberFormat, NumberFormatInfo> ResolveNumberFormats(
+        private static Dictionary<IXLNumberFormatBase, NumberFormatInfo> ResolveNumberFormats(
             WorkbookStylesPart workbookStylesPart,
-            Dictionary<IXLNumberFormat, NumberFormatInfo> sharedNumberFormats,
+            Dictionary<IXLNumberFormatBase, NumberFormatInfo> sharedNumberFormats,
             UInt32 defaultFormatId)
         {
             if (workbookStylesPart.Stylesheet.NumberingFormats == null)
@@ -3332,7 +3351,7 @@
                 });
             }
 
-            var allSharedNumberFormats = new Dictionary<IXLNumberFormat, NumberFormatInfo>();
+            var allSharedNumberFormats = new Dictionary<IXLNumberFormatBase, NumberFormatInfo>();
             foreach (var numberFormatInfo in sharedNumberFormats.Values.Where(nf => nf.NumberFormatId != defaultFormatId))
             {
                 var numberingFormatId = 164;
@@ -3368,7 +3387,7 @@
             return allSharedNumberFormats;
         }
 
-        private static bool NumberFormatsAreEqual(NumberingFormat nf, IXLNumberFormat xlNumberFormat)
+        private static bool NumberFormatsAreEqual(NumberingFormat nf, IXLNumberFormatBase xlNumberFormat)
         {
             var newXLNumberFormat = new XLNumberFormat();