How Sri Lanka's NIC Number Works — Format, DOB & Gender Explained

By Pubudu Tharanga · Last updated August 2026 · Not affiliated with DRP

Every Sri Lankan citizen receives a National Identity Card (NIC) number from the Department for Registration of Persons (DRP). The number is not random — it encodes the holder's date of birth, gender, and voter status using a compact numeric structure defined by DRP. This page explains exactly how it works, covering both the old 9-digit format and the new 12-digit format introduced around 2016.

1. The Two NIC Formats at a Glance

Old format (10 characters: 9 digits + V/X)

• Positions 1–2 (YY): Last two digits of birth year. Add 1900. So "90" → 1990.
• Positions 3–5 (DOY): Day-of-year code (1–366 for males; 501–866 for females). "673" → female, day 673 − 500 = 173 → 22 June.
• Positions 6–9: 4-digit serial number unique within that year and DOY group.
• Position 10 (V/X): V = voter-registered; X = not registered or exempted.

New format (12 digits, issued from ~2016)

• Positions 1–4 (YYYY): Full 4-digit birth year. No ambiguity — works for anyone born in 2000 or later.
• Positions 5–7 (DOY): Same day-of-year encoding as old format.
• Positions 8–11: A leading 0 followed by the 4-digit serial. The leading 0 was inserted to expand the serial space.
• Position 12: Check digit (numeric). Voter status (V/X) is no longer encoded.

2. How Date of Birth Is Encoded (Day-of-Year)

Instead of storing month and day separately, DRP stores the day-of-year (DOY) — a number from 1 to 366 counting from January 1.

To decode: if DOY > 500, subtract 500 to get the real DOY and mark gender as female. Then convert DOY to a calendar date by walking through month lengths, accounting for leap years.

3. Gender Encoding

The DRP uses a binary encoding in the DOY field:

• DOY 001–366 → Male
• DOY 501–866 → Female (actual DOY = encoded − 500)

There is no third option in the official DRP encoding scheme. The NIC number does not explicitly mention gender anywhere; it is implied entirely by whether the DOY field is above or below 500.

4. Voter Status (Old Format Only)

The final character of an old-format NIC is either V or X:

• V — Voter: the person is registered on the electoral roll.
• X — Non-voter: not registered, or has a DRP-recognised exemption (e.g., diplomats, certain disabilities).

New 12-digit NICs do not encode voter status. V/X was dropped when the format was redesigned because voter registration is now maintained separately by the Elections Commission.

5. Converting Old NIC to New NIC

The conversion formula is straightforward:

1. Prepend 19 to the 2-digit year (assumes all old NICs are 1900s births).
2. Keep the 3-digit DOY unchanged.
3. Insert a 0 before the 4-digit serial.
4. Drop the V/X suffix.
5. Append the check digit (the DRP compute this; for online decoding it is usually just provided as-is by the citizen).

Note: NICs for people born in 2000 or later were always issued in the 12-digit format.

6. Leap Year Handling

A year is a leap year if:

• It is divisible by 4, and
• It is not divisible by 100, unless
• It is also divisible by 400.

Examples: 1984, 1988, 2000, 2004, 2024 are leap years. 1900, 2100 are not. If DOY = 060 and the year is not a leap year, that is an edge-case in the original DRP record — NIC Info will still attempt to decode it gracefully.

7. The Check Digit (New Format)

The 12th digit of a new-format NIC is a check digit. DRP has not published the official checksum algorithm publicly, but community analysis and cross-referencing with DRP data suggests it uses a weighted modulo scheme similar to Luhn. For the purposes of decoding DOB and gender, the check digit is not needed — only digits 1–11 matter.

8. What the NIC Does NOT Tell You

• Full name or address — not encoded.
• Province or district of birth — not encoded (sometimes confused with serial range, but DRP has not published a definitive mapping).
• Current voter status — the V/X in old NICs reflects registration at the time of issue, not current status.
• Religion, ethnicity, or marital status — none of these are in the number.

9. Frequently Asked Questions