Missing Character Solver

How Missing Character Solver Works?

The Missing Character Solver tries each allowed character in the unknown position. The candidates may be digits or letters. It returns the characters that leave the checksum valid.

1. 1Type the alphanumeric code and put ? where the unreadable character sits.
2. 2Select the scheme so the tool knows the allowed character set.
3. 3Substitute each allowed character in turn.
4. 4Validate each candidate.
5. 5Return all passing characters, with their count.

Missing Character Solver Formula

The solver formula is Solutions = { c ∈ Alphabet : valid(code with ? = c) }.

Solutions = { c ∈ A_scheme | valid_scheme(code[? := c]) }

• A_scheme is the allowed character set (for example 33 characters for a VIN).

Candidates tested = 33
Passing characters = 7, G, P, X
VIN transliteration maps G, P, X, and 7 to the same value 7, so 4 characters pass

Missing Character Solver Conversion Table

The Missing Character Solver table shows the number of candidates that survive in 5 alphanumeric schemes.

What is Missing Character Solver?

A Missing Character Solver is a tool that recovers 1 unknown letter or digit in an alphanumeric identifier. The result shows every character that the checksum accepts.

Schemes that fold 2 or more letters into 1 value (VIN, ISIN) return more than 1 candidate. Schemes with a value per character (IBAN, ISO 7064) return 1.

What are the uses of Missing Character Solver?

There are 3 main uses of the Missing Character Solver, including VIN recovery, IBAN repair, and OCR correction.

• VIN recovery: Inspectors narrow down a corroded VIN character.
• IBAN repair: Payment teams fix a single unreadable IBAN letter.
• OCR correction: Developers resolve low-confidence OCR characters.