I think the max penalty is now two years. I had to bring a tag current on a vehicle (it was insured but had not been driven for a few years, so I didn’t bother with the tags), and I’m pretty sure they only charged me for two years of back tags.Just a heads up, you must re-new a black tag every year just like regular tags or you will end up with penalties. Folks have probably already said that, but I wanted to say it again. Had a vehicle that needed a very rare engine, finally found one good enough to rebuild. Had black tagged it and didn't understand it needed to be renewed every year. 3 years latter got it all together and was surprised by a $275.00 tag charge for a 1991 vehicle.