People are forgetful. Sometimes there’s nothing to be done about it. However, in the case of taxes, you can always correct a mistake, even if you’ve already filed.
A year’s worth of information is a lot to remember, and if you leave out a crucial piece of information that could alter you tax refund or tax bill, then you can file an amended tax return to correct any mistake — whether it be that something was incorrect, omitted or incomplete about the original tax return.
Taxpayers have a fairly generous window to amend a tax return, according to H&R Block, since the deadline is whichever is later of three years after the original deadline or two years after taxes were paid for that year.
If you’ll owe more in taxes, the sooner you amend the better
— otherwise you could find yourself penalized by the government and pay more. H&R Block recommends that if you discover a taxable mistake and you e-filed your original return, give it time to be processed before amending it. And if you’re expecting a refund, you should submit your amended return after
you receive the refund.
Amended returns must be mailed in even if you e-filed the original return. The form to correct 104, 1040-A and 1040-EZ forms is the 1040X.
Oops! I Made a Mistake on My Tax Return, but I’ve Already Filed
– H&R Block