I've posted this in general as although it's for my coupe the process is the same for every car. I bought a private plate for my car and I have a 'certificate of entitlement' from the DVLA. The car is at Joe's and has just passed it's MOT ( ) but I have yet to tax it. Could anyone who has been through this process before just go through the best way to go about this. Specifically, if I tax the car now on it's current age related plate, will I need to re-tax it at the DVLA office later for the new reg and claim the unused months back on the old one?
A rough guide of the process would be great.

Download a V62 form from Dvla website and it'll guide you through the process

you will have to go in to your local dvla office and they will sort out the logbook and road tax while your there .

Thanks chaps

If you tax it and then re-register it, you will be issued with a new tax disc with the new reg for the balance of tax on the original disc.

Just bumping this as I have a query about my private plate. I know I can pay £80 or so to take the reg off a car and store on 'retention.' When I buy another car and I want to put the plate on that - Do I have to pay another £80 or so then as well?

You pay £105 now to put the plate on retention for a year. That is £80 for the retention and £25 to reassign it to a vehicle.

What happens if you do not put it on another vehicle within the year?

You pay to extend validity, but try not to forget otherwise you lose it (but you can write a grovelling letter and hopefully get it back). You can extend for 1 or more years in advance. I would imagine that most questions like this would be answered in an FAQ on the DVLA website?

Cheers Dave
I had thought about buying a 11 PP direct from DVLA but could not see what happened if you did not use it within 12 months...
PPs seem to divide opinion, but a good one is perhaps a good way of advertising a business, rather than just a status thing or perhaps a bit of fun?

Every year you get a reminder letter asking if you want to keep it on a retainer, then you pay about £25 to keep it on the retainer for another year (or you can pay for multiple years at once). As far as I know you can just carry on like that indefinitely, there is no time limit to getting it on a car as long as you keep paying the £25 each year.

Once you are ready to assign it to a vehicle you don't need to pay anything to do so, you just send the relevant paperwork off to DVLA.

I had a really nice private plate with my current car but I already had another private plate I wanted to assign to it. I don't want to lose the plate that came with the car in case I ever decide to sell, so I've just got it on a retainer and will continue to renew each year.

This has changed now to £80 for a 10 year retention.
It cost nothing to assign it to a new vehicle at any time within the retention period.

It is also £80 to swap from one vehicle to another.