Northern Irish Number Plates Explained
The I and Z plates: why they have never carried an age identifier, how to read the county code, and why they are the best-kept secret for putting a private plate on any car.
At a glance
- 1899Irish code allocation
- I / ZSignature letters
- 0Age identifier
- AnyVehicle age eligible
Three letters (two for older marks) that always include an I or a Z, then one to four numbers. There has never been a year letter or age code.
History of the format
When registration letters were allocated across the United Kingdom in 1903, the whole of Ireland was given the letters I and Z as its distinguishing characters, and each Irish county received a two-letter code containing one of them. After partition Northern Ireland kept the system, and as counties exhausted their two-letter series they added a third letter in front, exactly as Great Britain had done in the 1930s.
Crucially, Northern Ireland never adopted the suffix or prefix year letters or the 2001 age identifier. Marks are still issued today by DVLA in the original letter-and-number style, which means every Northern Irish registration ever issued is dateless.
Since NI and GB registrations became fully transferable, Northern Irish plates have become the affordable route to a dateless look — and the only way to get the letters I and Z onto a private plate.
Letters that were never used
Q is not used, and because a Northern Irish mark must contain I or Z you will never see a “clean” three-letter group like ABC. Letters were assigned by county rather than year, so some combinations simply never reached issue. The absence of I in modern GB plates is exactly why initials like IAN or ZOE are only possible on a Northern Irish plate.
Regional codes and memory tags
The two-letter code (the last two letters on a three-letter mark) identifies the county or city that issued the mark. Belfast, as the busiest authority, has by far the most codes.
| County / city | Codes |
|---|---|
| Antrim | IA · DZ · KZ · RZ |
| Armagh | IB · LZ · XZ |
| Belfast | OI · XI · AZ · CZ · EZ · FZ · GZ · MZ · OZ · PZ · TZ · UZ · WZ |
| Down | IJ · BZ · JZ · SZ |
| Fermanagh | IL |
| Londonderry | IW · UI · NZ · YZ |
| Tyrone | HZ · VZ |
Which vehicles can carry this format
A Northern Irish plate has no age identifier, so it can be assigned to any vehicle registered in Great Britain or Northern Ireland, of any age — a 2025 electric car or a 1980s classic. The normal transfer rules apply: the vehicle must be registered with DVLA, taxed or SORN, and available for inspection if requested.
Buying tips
- NI plates are the cheapest way to get a dateless plate that can go on any car — often a fraction of a GB dateless equivalent.
- Look for I or Z that fits a name: KIM, TIM, LIZ, ZAK, JIZ and countless initials are possible here and nowhere else.
- Low numbers (1–99) on an NI mark are collectible and appreciating steadily.
- Because they never date, an NI plate can move with you from car to car indefinitely.
Northern Irish Number Plates Explained: FAQ
Can I put a Northern Irish plate on my car in England?
Why do Northern Irish plates have I or Z in them?
Do Northern Irish plates show the age of the car?
Are Northern Irish plates cheaper than dateless GB plates?
The Other Formats Explained
Every UK registration belongs to one of five families.
Dateless Number Plates
Suffix Number Plates
Prefix Number Plates
Current Style Number Plates
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