No worries, just file an amended return (1040x). This is a perfectly normal thing to do, and could save you money, or correct a problem that the IRS will find anyhow.
Let’s say you forgot to report a W2 — it’s no problem to file 1040X and report that income and withheld tax — you may get a bigger refund. However, if you don’t file an amended return, rest assured that the IRS will catch the error via their computers — and you’ll get a letter from them with the corrections.
For more information on filing amended returns, see this article, or call us at Denny & Company.