The general rule on internet sales is that if the vendor has a brick and mortar facility in a state, then they have to charge sales tax. It doesn't have to be a retail location, a warehouse or office meets the criteria.
MTC has on location in Texas. If I bought from them when I lived in Massachusetts I wouldn't pay tax. Now that I live in Texas if I buy from them either in person or via the internet, they have to charge tax.
If, OTOH, I bought from You Do It Electronics in MA, they wouldn't have to charge me sales tax. Well, unless Taxachusetts has figured out a way to make them charge sales tax. They tried that several years ago when MA residents went to NH to buy tires from a company with stores in both states. I forget how far up the courts that one went, but MA lost. They also threatened to send state troopers to NH liquor stores to monitor vehicles with MA plates and charge the owners with importing alcohol. In that case the NH governor ordered that NH troopers should arrest MA troopers trying to apprehend MA resident in NH for violating some MA law.
Got that? I just threw it in because it was funny at the time.
If there is a state somewhere that doesn't have an Amazon facility then they don't have to charge sales tax. Again, it doesn't have to be a store (not that they have those any longer) it can be a data center, warehouse, whatever.
Here is a pretty good reference for those interested.
uniden.com
