Typically the IRS has three years after you file your return to perform an audit, and sometimes up to six years. But what exactly triggers this statute of limitations?
Filing Early. If you file early (say March 1), the statute runs from the due date (April 15).
What’s Filing? This is pedestrian, but what counts as “filing”? It matters any time you’re talking about the statute of limitations, so it isn’t a silly question. For many these days, filing is hitting send, filing electronically. You should keep a print of everything, including the IRS response.
If you use the mail–I’m still a fan of mailing paper returns when
possible–it’s timely mailing. Whether you send via US Mail or by a private courier service like FedEx–keep proof of mailing! See IRC § 7502(f).
That means certified mail return receipt requested, or a copy of the FedEx waybill and receipt. Private postage meters? You don’t have proof of mailing if you use a private postage meter in your office.
Lost Returns? What if the IRS never receives your return? The rule that timely mailing is timely filing doesn’t apply if the return never arrives. For that reason, you’ll not only want proof you sent it but proof the IRS received it. See IRC § 7502(c). If the IRS loses it afterword, you’ll be asked to provide a copy and to show that you sent it and the IRS received it.