EDIT: I do wish MA had a temp tax ID like MD though
You and me both.
I'm not sure if this has been made entirely clear, but there's a 'show promoter' license that we, as an organization need to fill out (else we run into problems). Part of that is a section on sales tax IDs for all vendors. If you're selling anything, you're a vendor.
In the past, there was an exception built into the law that set a threshold of a minimum of 3 shows in a calendar year before a show promoter license was required. That exception was removed, so we're required to collect this information from anyone selling anything. In the past, I've collected this kind of information from everyone in the Dealers' Room, since I figured it'd be smart to do so in case of some kind of cataclysmic audit or something. Also, they'd already be taking care of that kind of thing, anyway.
I can't find any information on any "seasonal filing" at all. That was only in a search on the DoR's site. When I called them a while back to figure out if there was any kind of alternative to make it easier (as in any way similar to MD or any other state) I was told that there really isn't and that the registration is at least a permanent one, so the 'growing pains' should be largely limited to this year.
I can't say for certain that if you talk to one specific person at the MA DoR you'll get one answer and if you talk to another person you'll get another answer. Any question specifically about an EIN really should be answered by the IRS, not the MA DoR.
When I called the DoR, it was to get answers about some questions and they answered everything I asked. At the same time, I was coming to my list of questions from my own perspective as the guy that has to fill out the show promoter license paperwork. I tried to anticipate some of the questions I thought would be most obvious, but I guarantee I couldn't anticipate everything. We can try calling the DoR and ask them questions, but the best solution is probably to call them and make sure you've got answers to your own questions.
It is a system that's very different from ones that I've seen in other states. Unfortunately, that basically means that we're all caught in this arcane setup together.
Like Mara mentioned, the EIN can be used for identification purposes. That was actually the one 'hint' that the MA DoR mentioned that seemed useful. It's possible to set things up for like payroll taxes and whatnot, but if you have no payroll, you don't need to worry about that. Either way, if you've got questions, the ultimate answers will come from either the MA DoR or the IRS.