In the new version of the ID card, the number 15-17 is the sequence number, of which 17 (the penultimate) male is singular and female is double. It is no longer possible to judge the man and the woman with the last digit (18th) of the ID card.

18 bits are check digits, 0-9 and X. As the check code of the tail number, it is calculated by bringing the first seven digits into a unified formula. The result of the calculation is 0-10. If someone’s tail number is 0-9, X will not appear. But if the tail number is 10, then you have to use X instead, because if you use 10 as the tail number, then the person’s ID card becomes 19 digits. X is the number 10 of the Roman numeral, and X is used instead of 10.

Calculation method

- Multiply the 17 digits of the previous ID number by different coefficients. The coefficients from the first to the seventeenth are: 7-9-10-5-8-4-2-1-6-3-7-9-10-5-8-4-2.
- Add the result of multiplying these 17-digit numbers by the coefficients.
- What is the remainder by adding and dividing by 11?
- The remainder may only have 11 digits of 0-1-2-3-4-5-6-7-8-9-10. The number of the last ID card corresponding to it is 1-0-X -9-8-7-6-5-4-3-2. (ie, the remainder 0 corresponds to 1, the remainder 1 corresponds to 0, and the remainder 2 corresponds to X…)
- through the above, if the remainder is 3, it will appear on the 18th digit of the ID card is 9. If the corresponding number is 2, the last digit of the ID card is the Roman numeral X.