We used estimates extensively (on a 2019 1120S.) Very unusual circumstances justify it. I have not filed it yet. Have you ever voluntarily disclosed estimates? What was the IRS response, if any?
Not estimates, but I've disclosed other stuff on Form 8275. It's always handy to have your thought process well laid out in writing at the time, in case you need to figure out what you did and why in the future. IRS has never said or done anything.
