Sri Lanka Vehicle Number Plate Decoder

Sri Lankan vehicle plates carry three pieces of information encoded in the letters and digits: which province first issued the plate, the vehicle's class, and a sequential running number. The decoder runs a deterministic six-step pipeline against the input — no remote lookup, no model, no guesswork beyond the era band.

1. Normalise. Uppercase the input, strip whitespace and hyphens, and drop the legacy leading SRI token if present. Reject anything that has characters outside A–Z and 0–9 after normalisation.
2. Detect format. Match in priority order:
   • ^(WP|CP|NP|EP|NW|NC|UP|SG|SP|NE)([A-Z]{2,3})(\d{1,4})$ — province-prefix format.
   • ^([A-Z]{2,3})(\d{4})$ — national series.
   • A pre-1981 numeric form (digits-first, optionally with SRI) — recognised and rejected as retired.
3. Province lookup. If the plate is in province-prefix format, the first two letters resolve to one of nine current provinces (plus the legacy transitional NE code).
4. Class lookup. The 2- or 3-letter class block resolves to a vehicle category from the DMT-published class table — motor car (C-block), van / lorry (K-block), bus / coach (BAA–BMZ), land vehicle (L-block), motorcycle (J-block for heavy, EP for light), trailer (P-block), goods carrier (G-block), and the three-wheeler series RE → TH → XA.
5. Era estimation. For national-series plates, the (first letter, second letter) pair indexes into an era table derived from successive DMT annual statistical reports. Province-prefix plates are tagged with the broader 1981–2000s era band instead.
6. Cross-check.The class is also classified by an independent first-letter rule. When both methods agree, the result is marked “cross-checked” for credibility. When the class falls outside our table, the decoder is honest — it returns a structural decode and flags the class as “not in table.”

What the decoder does NOT do: owner lookup (DMT does not publish this), VIN / chassis matching, revenue licence status, or real-time validation against the DMT register. The decoder works on the plate string alone — anything more requires the registration certificate or a direct DMT divisional office visit.

• Department of Motor Traffic — Vehicle Registration Information
• DMT — Vehicle Class Categorisation (annual statistics)
• Motor Traffic Act (Chapter 203) — statutory framework
• Department of Motor Traffic — official portal

The province and class tables on this page were last cross-checked against the DMT publications on 2026-05-16. The era bands are reviewed annually against the latest DMT statistical report.