code: private boolean checkSiVatId(final String pvatId) {
      boolean checkSumOk;
      final int checkSum = pvatId.charAt(9) - '0';
      final int sum = (pvatId.charAt(2) - '0') * 8 + (pvatId.charAt(3) - '0') * 7
          + (pvatId.charAt(4) - '0') * 6 + (pvatId.charAt(5) - '0') * 5 + (pvatId.charAt(6) - '0') * 4
          + (pvatId.charAt(7) - '0') * 3 + (pvatId.charAt(8) - '0') * 2;
      int calculatedCheckSum = MODULO_11 - sum % MODULO_11;
      if (calculatedCheckSum == 11) {
        checkSumOk = false;
      } else {
        if (calculatedCheckSum == 10) {
          calculatedCheckSum = 0;
        }
        checkSumOk = checkSum == calculatedCheckSum;
      }
      return checkSumOk;
    }
docs: check the VAT identification number, country version for Slovenia.
  
  @param pvatId vat id to check
  @return true if checksum is ok