code: private boolean checkDeVatId(final String pvatId) {
      final int checkSum = pvatId.charAt(10) - '0';
      int sum = 10;
      for (int i = 2; i < 10; i++) {
        int summe = (pvatId.charAt(i) - '0' + sum) % 10;
        if (summe == 0) {
          summe = 10;
        }
        sum = 2 * summe % MODULO_11;
      }
      int calculatedCheckSum = MODULO_11 - sum;
      if (calculatedCheckSum == 10) {
        calculatedCheckSum = 0;
      }
      return checkSum == calculatedCheckSum;
    }
docs: check the VAT identification number, country version for Germany.
  
  @param pvatId vat id to check
  @return true if checksum is ok