How do you get it to the NOT by road legally without a tax disc. I had to tax my change of car privately for 3 months when changing as it was an import. Even if any car is even off the road now you need police permission not to have it taxed even if its sitting in your drive.
You generally can't tax a car as soon as you buy it as you have to wait for the VLC to come back from Shannon. The Gardai make allowances for recently purchased cars and, as Tony notes, you will be liable for arrears from the change of ownership date recorded in Shannon so even if you are charged, provided you pay the tax (including any arrears) and the offence was allegedly committed within a month of change of ownership, there will be no loss of revenue to the State so the charge would most likely be struck out or dismissed the Probation of Offenders Act 1907.
The new rules removed the anomaly that allowed one to declare a vehicle as off the road retrospectively. That actually serves to ensure that arrears are collected so reduces the amount of Garda scrutiny required. In the old days you just had to fill in a form and get it stamped at a Garda station to "prove" the car had been off the road hence it was possible to get a new form every month, keep it in the car and never pay any motor tax.
