About a week e-filing my taxes this year one of my brokerage accounts sent me a corrected 1099-div. Is there a deadline to get my amended tax forms sent in? Is it still April?
Also, are is there a de-minimis limit for how substantial the change is before I am required to amend my filing?
The deadline to file an amended return is 3 years after the unextended due date, or 3 years after the date you actually file if later, or for refund only 2 years after payment if later (which can happen only if you paid significantly late, already a bad situation to be in).
However, if you owe (more) money, the deadline to pay without penalty and interest is the unextended due date (April 15, or in years where that is a weekend day the next business day).
Thus if the correction increases your tax, it is best if you pay by April 15, and since you need to have completed the return to determine the payment, you might as well file the return. If you don't do so reasonably quickly -- maybe a month -- I think they will 'time out' the payment and return it, and then you've lost at least some of the benefit of paying timely. Although if the increased tax is fairly small, the penalty (only FTP) and interest for a month or two will be small too, and from your point of view that may be reasonable to let you do it more conveniently.
If the correction decreases your tax, you can wait up to April 2023, although I don't recommend it. You also have the option of doing nothing; you aren't required to claim a refund, or in general any decrease in tax, that you are entitled to.
AFAIK there is no official de-minimis amount for amending. I think I saw in a ETAAC report, or maybe TIGTA, that it costs them about $20 to process a 1040X (because it's on paper), so on their side there's no benefit in you filing an increase smaller than that (and on your side it's pure cost, of course). Given their workload, I'm sure the actual threshold to do anything at all about an 'AUR' discrepancy, even a 'soft notice', is higher, but we don't know by how much, and it could vary.
