VRT

Hi guys, I'm hoping some of you can help me.

I bought a car in the North in April and I went to the NCT Centre to pay the VRT the first opportunity I had, which was about 2 weeks after I bought it. Unfortunately I was missing a document which the previous owner of the car had. When I contacted the owner again he advised me he had posted it away and that the DVLA would send it to me. I ended up having so much hassle trying to get this bit of the tax book from the man but eventually got it about 3 weeks ago. In the meantime I was stopped by the Customs in June and explained to them I had tried to pay the VRT but was missing a document and would take the car across as soon as I got it. This was fine with them, they took my details and followed up with a phone call to me some time in August to see if I had taken the car through. My circumstances changed early September and I have a new job now with a company car. Because I don't actually need my car now and the man I bought the car from turned me off it (he really was a nightmare, I have no idea why he held on to the tax book so long, anyone shed any light on that?! Personally I think he was just an awkward pr*ck!) so I decided to sell the car. I put it up for sale and have agreed to sell it to a woman from Armagh (I have accepted a deposit for it) and she will be collecting it this weekend.

But someone I work with mentioned that I am technically still eligible to pay the VRT. Is this correct? Even though the car is staying in the North now and won't be taken across, because I had it here for a few months do I need to pay the VRT? I'm not trying to avoid paying it or anything and I don't want to get in trouble, I just want to make sure I go about things the right way. Someone else suggested I might just have to pay the late fine? Will the woman I sell the car to have any problems as a result of all this? Thanks for your help