The standard rule is three years. The IRS has three years from the date you filed your return or the return’s due date, whichever is later, to start an audit. So if your business return was due March 15 and you filed it March 5, the clock doesn’t start until March 15. If you filed late on August 20, the three-year window starts on August 20. This is the rule that applies to most small businesses in most situations.

That window doubles to six years if you understate your gross income by more than 25%. This doesn’t require any intent to deceive. Forgetting to report a significant income source, misclassifying revenue, or making a large error on your return can push you past that 25% threshold. Many business owners don’t realize how easily this can happen, especially if they have multiple income streams or sloppy recordkeeping throughout the year.

If you file a fraudulent return or never file at all, there is no statute of limitations. The IRS can audit you ten or twenty years later. This is why filing a return you’re unsure about is always better than not filing. A late or imperfect return at least starts the clock running. No return means the clock never starts.

One common point of confusion involves extensions. Filing an extension to push your deadline from March to September doesn’t extend the audit window beyond three years. The statute simply starts from your actual filing date. However, if the IRS asks you to sign Form 872 during an active audit to extend the statute, and you agree, that does push the deadline further. You’re not required to sign it, but refusing can sometimes prompt the IRS to make a quicker and less favorable assessment.

Because of these overlapping timelines, the safest practice is to keep all supporting records for at least seven years. That covers the six-year window with a buffer. This includes bank statements, receipts, invoices, payroll records, and any documentation that supports what’s on your return. Digital copies are fine as long as they’re organized and accessible. If you work with a Houston fractional CFO or bookkeeper, they can help you set up a system so nothing gets lost.

The reality is that most small business audits happen within the first two years after filing. The IRS tends to act relatively quickly when something triggers a review. But “most” isn’t “all,” and the three-year and six-year rules exist for a reason. Having clean books and organized records means an audit is an inconvenience rather than a crisis. If you do receive an audit notice, tax audit support from someone who understands IRS procedures can make a significant difference in how smoothly the process goes and how it ultimately resolves.