You’re probably not intentionally trying to hide income from the IRS, but you may be worried about some sloppy bookkeeping or paperwork you’re unsure you filled out properly. A lot of people wonder how long they need to hold onto receipts and records, to prove income and expenses. 

Forbes recently published an article outlining the IRS statute of limitations and how a tax evasion or fraud claim by the IRS can change a case. Here’s what you need to know.

The basic rule is that the IRS has three years after you file to audit you. But if you’ve failed to report 25% or more of your income, the IRS gets twice that amount of time. On top of that, statutes are sometimes extended, and the IRS can request that you sign a form to allow an extension. If you refuse to sign the form, you’ll raise eyebrows, but you can try to limit the time or scope of the extensions.

Normal limitations don’t apply if you file a false return under-reporting income, or if you fail to file. In those cases, the stakes on all counts are raised substantially. You’ll face potential criminal charges and prison. 

Section 6531(2) of the tax code says the statute is six years commencing once the return is filed, or from the time you willfully failed to file a return. In a case of alleged criminal tax evasion, that means the statute hasn’t run if the taxpayer is indicted within six years after “willfully attempting in any manner to evade or defeat any tax or the payment thereof.” Some courts have concluded that the six year statute doesn’t even start to run until the last act of tax evasion.

The reality is, if you’re intentionally hiding money, filing false returns, or failing to file at all, you need to worry for a long time. In fact, for civil tax fraud, there is no statute of limitations–the IRS can come after you at any time. But if you’re doing your best and just miss a receipt here and there, or forget to record a small payment from a client, you’re probably safe after three years.

In any case, you’ll want to get professional advice on how to handle an audit.