Depending on what it is, you usually can amend your taxes for a full year after they're sent in.
More likely than not, you can put in a little effort and help your folks out.
Otherwise, it's just a few thousand dollars. It might sound like a lot at first, but it's not.
I'm a parent of 3 children. And if all they cost me was a few thousand dollars, then I'd be a rich man. :)
If you want some specific advice, you could tell us more about what exactly was going on if it's appropriate to tell folks.
It's not income taxes. She doesn't even pay thousands in income taxes total, much less a mistake making that much of a difference.
It's real estate taxes, and because of her age, she is exempted in our county.... but you have to file an annual form to be eligible. And that form is due April 1. And I completely forgot.
So, instead of her real estate taxes being zero, as it has since she reached the age of exemption (70 IIRC but no longer really remember that) she will now owe 100% of her real estate taxes, which is above $7,000.
No tax preparer in the world can help with that. And while she's not poor, this is, and will be, a MAJOR HIT to her, living only on social security and pensions.
No, there is no making up on this one, no forgetting laughing about it later, this will affect her directly, all because of me, and I just can't stand living with the thought of that after all she, Dad when he was alive, and the rest of the family have done for me since becoming disabled Nov 24, 1999.
I am just so not going to be able to deal with this I think...