if you return has been accepted I don't think you should be too concerned about whether the 8453 made it by today.
Personally, I doubt they even look at this below a certain threshold, or that you will ever hear about this again, and this PO BOX is probably inundated with mailings from TT users, likely exacerbated this year by all the problems with importing 1099s. From what I've seen in this forum, a lot of this 8453 is avoidable, TT encourages jamming all 1099s into sales summaries, but any adjustment to a summary will then trigger this 8453 mailing as it is missing the details. This is avoidable by entering these adjustments/exceptions (wash sales, AMD, noncovered categories) as "one by one" (and the remaining balance of the 1099 as a clean unadjusted sales summary) which sends the detail electronically on Form 8949 with your return.
as for payments @buteo35 was concerned about his check, if able going forward you can pay electronically and this will likely be mandated going forward as Trump issued exec order to largely eliminate checks from this process. I've been paying electronically for some years, no vouchers, no USPS. Just beware the IRS debits quickly, it will happen overnight after you enter it so ensure the money is in the account. State likely has equivalent process also.
https://www.irs.gov/payments
https://www.whitehouse.gov/presidential-actions/2025/03/modernizing-payments-to-and-from-americas-ba...
