As you should but it is a bit of an honor system and a lot of people don't even know you are supposed to do it. I see tons of Massachusetts plates at the mall a

As you should but it is a bit of an honor system and a lot of people don't even know you are supposed to do it. I see tons of Massachusetts plates at the mall and I guarantee you most of them won't be writing a check to the MA Department of Revenue. The process of having the seller withhold the tax is much more effective in getting people to actually pay and that is the system a lot of states that rely on sales tax are pushing for.