IRS is very understanding, but I wouldn't suggest this. I have gotten plenty of letters from the IRS and they are always stressful. The IRS has always responde

IRS is very understanding, but I wouldn't suggest this. I have gotten plenty of letters from the IRS and they are always stressful. The IRS has always responded in a really positive way, so it is really worth talking to them (well, unless you think you may be in real legal trouble... I guess "don't talk to the cops" applies here too...) if you're in the situation where you think "oh, yeah I messed up" or "oh, yeah they messed up" it's probably best to just reply... but yeah if you think it is serious talk to a tax attorney... (not an accountant, which isn't a tax attorney). The "they messed up" for me was a crypto thing, where I actually took a small net loss, and didn't file (because you don't need to, for capital losses, from my understanding, though I guess you should) and they thought I took some insane gain b/c of the $ value of the trades. I just mailed them the trades, said "I didn't submit the form for this b/c I didn't think I needed to for a loss" and they said "yay, thanks, see ya" a bit later. Positive experience.