How to check if a social security number is valid ??

Problem/Question/Abstract:

How to check if a social security number is valid ??

note : only tested on the dutch social security numbers

Answer:

function CheckFiscaalNumber(Value: string): boolean;
var
  n1, n2, n3, n4, n5, n6, n7, n8, n9: integer;
  s1, s2, s3, s4, s5, s6, s7, s8: integer;
  totaal, rest: integer;
begin
  if StrToInt(Value) > 10000000 then
  begin
    if Length(Value) >= 8 then
    begin

      if Length(Value) = 8 then
      begin
        Value := '0' + Value;
      end;

      n1 := StrToInt(copy(Value, 1, 1));
      n2 := StrToInt(copy(Value, 2, 1));
      n3 := StrToInt(copy(Value, 3, 1));
      n4 := StrToInt(copy(Value, 4, 1));
      n5 := StrToInt(copy(Value, 5, 1));
      n6 := StrToInt(copy(Value, 6, 1));
      n7 := StrToInt(copy(Value, 7, 1));
      n8 := StrToInt(copy(Value, 8, 1));
      n9 := StrToInt(copy(Value, 9, 1));

      s1 := n1 * 9;
      s2 := n2 * 8;
      s3 := n3 * 7;
      s4 := n4 * 6;
      s5 := n5 * 5;
      s6 := n6 * 4;
      s7 := n7 * 3;
      s8 := n8 * 2;

      totaal := s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8;
      rest := totaal mod 11;

      if rest <> n9 then
      begin
        Result := False;
      end
      else
      begin
        Result := True;
      end;
    end
    else
    begin
      Result := False;
    end;

  end
  else
  begin
    Result := False;
  end;

end;