I’ve been thinking of paying mine in july this year. Wondering if it’s worth the extra headache
The SOT is simply a tax paid to deal, import or manufacture NFA firearms. The license is your ticket to receive across state lines and dispose of in your state. Also note, if you are an FFL/SOT, you may take MGs, SBR, SBS, and DDs across state lines w/o permission from the NFA branch (5320.20) just make certain where you are going you can have them under state/local law.
If you pay it, make sure of two things. First, be absolutely certain you have a registration form for every item transfered in, out, and currently in your possession. I would be very surprised if you get inspected and the print out the IOI has from the NFA branch is completely accurate. Bound book has the correct number of NFA items, all have forms, closed entries for approved transfers out, open entries for NFA items in inventory. Make sure you do a 4473 to a buyer if not licensed. Assuming your state uses FBI for NICS, you do not need to call NICS for a transfer approved to an individual, all others (Corp, trust, LLC, etc.) require NICS. Also note, if you a transferring a Title I firearm w/an NFA firearm, i.e. integrally suppressed pistol/rifle, or a pistol w/a can, the Title I firearm requires NICS even if transfered on the same 4473 with the approved NFA firearm. Some guys call in all 4473 transfers, even if exempt from NICS. I was told by my local ATF office not to do this if NICS exempt otherwise it was "misuse of NICS."
Second, if you pay the SOT, make sure you have either tax paid transfers or qualified tax exempt transfers. It is frowned upon to pay the SOT and aquire NFA items w/o tax paid to the .gov