diff --git a/VatFormatValidator.cs b/VatFormatValidator.cs
index d522fe3..748a0b6 100644
--- a/VatFormatValidator.cs
+++ b/VatFormatValidator.cs
@@ -49,7 +49,11 @@ namespace FCS.Lib.Utility
         /// <returns>bool indicating if the vat number conform to country specification</returns>
         public static bool CheckVat(string countryCode, string vatNumber)
         {
+            if (string.IsNullOrWhiteSpace(vatNumber))
+                return false;
+
             var sanitizedVat = SanitizeVatNumber(vatNumber);
+
             return countryCode.ToUpperInvariant() switch
             {
                 "DK" => ValidateDkVat(sanitizedVat),