That caught me last year. The K-1 came about three weeks after I'd filed my Fed and state taxes.
That called for an amendment. Amended the Fed, but forgot to amend the state. A couple months later
I got a nastygram from the state, with a penalty of a couple bucks. Oh well, live and learn.
I have my taxes done by an accountant, a couple years ago I picked
them up with the efile sheet for the wife and I to sign.
I returned the efile sheet, got home and checked the mail box, there was
an amended 1099! I immediately called the accountant, they had already
efiled, I had to do an ammended 1040. I have got ammended 1099s in mid
March a few times.
Now, I don't have my taxes done until later March.
Mikek
I think I told you guys, I just got my refund from 2011 or something
along with a $571 interest check I had to declare as income. That was
an amended return too. I had even forgotten the refund had not arrived
yet. I amended the return within weeks of the original but that
screwed them up for 5 years or something