Checksum letter

A checksum letter is alternative to checksum number. The difference from checksum number is the use of a letter as a check digit instead of a number. It is found in some FCVs and some LDIs.

Singapore licence plates
The checksum letter is calculated by converting the letters into numbers, i.e., where A=1 and Z=26, potentially giving seven individual numbers from each registration plate. However, only two letters of the prefix are used in the checksum. For a three-letter prefix, only the last two letters are used; for a two-letter prefix, both letters are used; for a single letter prefix, the single letter corresponds to the second position, with the first position as 0. For numerals less than four digits, additional zeroes are added in front as placeholders, for example "1" is "0001". SBS 3229 would therefore give 2, 19, 3, 2, 2 and 9 (note that "S" is discarded); E 12 would give 0, 5, 0, 0, 1 and 2.

Each individual number is then multiplied by 6 fixed numbers (9, 4, 5, 4, 3, 2). These are added up, then divided by 19. The remainder corresponds to one of the 19 letters used (A, Z, Y, X, U, T, S, R, P, M, L, K, J, H, G, E, D, C, B), with "A" corresponding to a remainder of 0, "Z" corresponding to 1, "Y" corresponding to 2 and so on. In the case of SBS 3229, the final letter should be a P; for E 23, the final letter should be a H. Note that letters F, I, N, O, Q, V and W are not used as checksum letters.

There is an online calculator for the checksum.

Checksum suffix letters are not applied to special government vehicles and event vehicles.

Other

 * The last digit of the NIE (Spain's national identification number). Based on modulus 23.
 * The final letter encoded in a six-letter mision code of Baytown Commuter Rail - using Luhn mod N algorithm.
 * The last character of a 10-digit Permanent Account Number, used in India.
 * The last digit of the fleet number section in the buses of Baytown. Note that Baytown uses checksum letter. Checksum suffix letters are not applied to buses of other states or cities in Econesia's fleet numbers, they use check digits, either modulus 10, modulus 11 or modulus 97-10. Baytown uses modulus 23.
 * The Irish Personal Public Service Number. ('W' is allocated to remainder of 0.)
 * The Albanian national identification number.
 * Italian fiscal code number, based on modulus 26, taken from all letters of the alphabet.
 * The last character of the Australian Medicare Provider Number (only A, B, F, H, J, K, L, T, W, X, Y).

FCV

 * The last digit encoded in Patestin, created by BartToons.
 * Unicornsmile's FCV for fictional characters.
 * The last character encoded in JimmyandFriends' File Number.

LDI

 * The Princess Clio Code, created by Princess Clio, a character from Sofia the First. The checksum letter is placed after the numeric check digit. Based on modulus 19, F, I, N, O, Q, V and W are not used as checksum letters.
 * The first character of the Miles Registration Number.
 * The last character of the Cinderella's LDI.
 * The final character encoded in Tomoka Minato's FCV, based on modulus 24.