AFAIK the place where the car is normally parked overnight is the "residence" of the car. If so, you need to pay the VRT and register the car at your home address.
I don't think you can obtain car tax in NI without a NI address.
I know someone living in the Border region who bought a NI car and didn't re-reg it as he was working the in North. That arguement did not impress the Customs and Excise people who called to his door and told him to have it re-registered or they would impound it.
What exactly are you suggesting? I agree you see a lot of NI registered cars in those counties. You see a lot of ROI registered cars in Fermanagh, Tyrone and Armagh too. Nothing unusual about that - I've seen Cork-registered cars in Kerry too...
"I have a relative from NI. He has a NI reg'd car for two years now. Lives and works in the South. Also has an NI address (family)....seems to work!"
Some people dont get caught, but it is still against the law, and if the customs and excise people do catch him, he will be told to re-register the car immediately, or risk the car being impounded.
He may not actually owe VRT depending on how long he has owned the car.
most people living in the border regions in the south will usually be using a relatives or friends address in the north.
Customs regularly have checkpoints at the border crossings and normally at the 8am times when people are travelling from the south to teh north for work. I've seen it plenty times on my route from Buncrana to Derry. All the NI regs get pulled in.
I suppose as long as you have all your ducks in a row and an answer for them every time as to why you are coming from the south in the morning, its possible to get away with it.
Well I don't have any statistics to hand, but I'd say there are probably more NI residents working in the ROI than ever. Perhaps these individuals hold on to their NI registrations for as long as possible?