Ongoing Vehicle Registration Number — Sri Lanka (DMT)

Since July 13, 2013, when CAA 0001 went into issue, every Sri Lankan registration number has the shape L1 L2 L3 NNNN. The first letter is the vehicle class and never changes within a class: C for motor cars, B for motorcycles, A for three-wheelers, D for dual-purpose vehicles, L for lorries and buses, R for land vehicles. The second and third letters run A to Z, and the four digits run 0001 to 9999. Zero is never issued, so a letter block holds exactly 9,999 numbers — not ten thousand. That single detail is where almost every hand-calculation of a plate gap goes wrong.

Province letters — WP, SP, CP and the rest — are not part of the sequence. They recorded which office issued the plate, and new issues stopped carrying them on January 1, 2023. The calculator strips them before doing anything else, so WP CBH-1234 and CBH 1234 resolve to the same position.

The sequence is a plain odometer, which means any plate can be converted to an ordinal index — its position counting from the very first number in its class:

index(L1 L2 L3 NNNN) = ((L2 − 'A') × 26 + (L3 − 'A')) × 9999
                       + (NNNN − 1)

Because CAA 0001 comes out as index 0, the index is also a running count of everything registered in that class under the three-letter system. The gap between two plates is then a subtraction and nothing more: gap = index(ongoing) − index(your plate). That figure is exact. If it comes out negative, your plate was issued after the reading was taken, or it is a reserved or personalised number allocated outside the running sequence.

Turning the gap into time is the one approximate step, and the page labels it as such. Dividing the gap by the number of vehicles of that class registered per month gives a rough elapsed period. The rates used here come from published Department of Motor Traffic registration data — for cars that is 2,652 to 5,752 registrations in August 2026 — and are shown as a band rather than a point, because sport utility vehicles are counted separately in that series and may register as cars or as dual-purpose vehicles, and because monthly volumes swing sharply with duty and credit policy. Reserved numbers, batch issuing and the 2020–2022 import freeze all blur the conversion further. For an exact first-registration date, read the vehicle's certificate of registration or ask the DMT; for an era estimate from the letters alone, the Number Plate Year Checker is the tool for that job.

One class letter holds 676 blocks of 9,999 numbers, or 6,759,324 in total, after which the DMT opens a new class letter — which is how the older car letter K gave way to C. The calculator reports how much of that capacity the ongoing number has consumed, so the next letter change is never a surprise.

Every class runs an independent sequence, so an ongoing number is only comparable to a plate of the same class. These are the six classes that carry a running three-letter series, with the category name you pick in the DMT eService and the GovSMS code that returns the same figure by text message.

Categories from the DMT ongoing-number eService dropdown; SMS codes from the Government Information Centre GovSMS catalogue. Monthly registration rates are published for 2 of these 6 classes; the rest show no elapsed-time estimate unless you supply a rate.

• Department of Motor Traffic — View Ongoing Vehicle Registration Number (eService)
• Department of Motor Traffic — Enquire Ongoing Registration Number
• Government Information Centre — GovSMS catalogue (DMT ONG codes, short code 1919)
• Daily FT — Sri Lanka vehicle registrations, August 2026 (DMT data via HNB Stockbrokers Research)
• Department of Motor Traffic — official site

The sequence rules, vehicle categories and SMS codes on this page were cross-checked against the sources above on 2026-09-22. The ongoing numbers themselves are deliberately not cached here: they change every working day, and a stale figure presented as current would be worse than none. The two official channels return the live number in under a minute.