Transferring a private number plate to Northern Ireland
This information is no longer correct. DVLA processes have changed. Double transfer (detailed below) is no longer needed. Northern Ireland registration numbers can now be assigned to vehicles regardless of the location.
...can be done, though it's a little bit more involved.
If the registration number you want to transfer is on another car, then a straightforward transfer from vehicle to vehicle is all you need.
If the registration number is on a mainland GB Certificate (either a V750 Certificate of Entitlement or V778 Retention Document), then it cannot be transferred straight to a vehicle if the vehicle is registered in NI (Northern Ireland). First it has to be assigned to a vehicle registered on mainland GB, then transferred to to your car / motorbike / van / etc.
Double number plate transfer
Because there are two transfers involved, unfortunately that also means two DVLA / DVA fees of £80 each. And access to a vehicle on mainland GB.
Some number plate companies offer this specialist service to transfer a number plate to vehicle in Northern Ireland, and have vehicles available especially for the service. They will charge a fee for the additional service and the use of one of their vehicles.
How long does it take to transfer a number plate to Northern Ireland?
Because there are two number plate transfers needed, involving both the DVLA (Swansea) and DVA (Coleraine), it takes a little longer than normal. You should allow around 6-8 weeks for the full transfer to be completed. Any specialist number plate company will take care of all the paperwork for you - so you don't need to worry about it.
What can I expect when the transfer is finished?
When the registration number transfer has been completed, you'll get a replacement tax disc, mot certificate (if applicable), and... up to 4 weeks later... a replacement V5 Registration Document. All the replacement documents will have the new private registration number.
Once you've received the replacement tax disc, you can go ahead and use your new private number plate on the car - no need to wait for the V5 Registration Document. BUT... don't forget to update your car insurance company!
Related article: Transferring private number plates in Northern Ireland