| AZ | Belfast |
| BZ | Down |
| CZ | Belfast |
| DZ | Antrim |
| EZ | Belfast |
| FZ | Belfast |
| GZ | Belfast |
| HZ | Tyrone |
| IA | Antrim |
| IB | Armagh |
| IG | Fermanagh |
| IJ | Down |
| IL | Fermanagh |
| IW | County Londonderry |
| JI | Tyrone |
| JZ | Down |
| KZ | Antrim |
| LZ | Armagh |
| MZ | Belfast |
| NZ | County Londonderry |
| OI | Belfast |
| OZ | Belfast |
| PZ | Belfast |
| RZ | Antrim |
| SZ | Down |
| TZ | Belfast |
| UI | Derry |
| UZ | Belfast |
| VZ | Tyrone |
| WZ | Belfast |
| XI | Belfast |
| XZ | Armagh |
| YZ | County Londonderry |
| LTZ | Buses built in Northern Ireland for Transport for London |
| QNI | Cars with indeterminate age, kit cars. |