Ireland PPSN Validator
Validate Ireland Personal Public Service Numbers (PPSN) using official Modulo 23 checksum rules.
About Personal Public Service Number (PPSN)
The Personal Public Service Number (PPSN) is a unique reference number used for access to public services, welfare benefits, and tax in the Republic of Ireland.
Issued by the Department of Social Protection and recognized by the Revenue Commissioners, it is required for employment, health services, and housing.
Anatomy & Structure of Ireland PPSN
The Irish PPSN consists of 8 or 9 alphanumeric characters structured as follows:
| Position | Field | Length | Meaning & Rule | Example |
|---|---|---|---|---|
| 1 to 7 | Serial Number | 7 digits | Sequential number allocated by the Department of Social Protection | 1234567 |
| 8 | Primary Check Character | 1 letter | Alphabetical check letter (A-W) calculated using Modulo 23 | T |
| 9 (Optional) | Secondary Character | 1 letter | Alphabetical character introduced post-2013 to expand address space | A |
Official Checksum Algorithm (Weighted Modulo 23)
Revenue Commissioners and DSP official checksum formula:
S = Σ(d[i] * (8 - i)) [i=0..6] (+ (ord(L2) - 64) * 9 if 9 characters); Remainder = S mod 23. Letter = map (0->W, 1->A..22->V).
- 1. Extract the first 7 digits of the identifier.
- 2. Multiply each digit by descending weights from 8 down to 2.
- 3. If a 9th character exists, add (alphabetical position of 2nd letter) * 9 to the total.
- 4. Sum all weighted values and compute modulo 23.
- 5. Map remainder: 1->A, 2->B... 22->V, and 0->W. The letter must match the 8th character.