In most situations, the IRS has up to three years to audit you after you file a tax return (or after the date when the return was due, if you filed early). However, if the IRS claims that you have unreported income exceeding 25% of the income you did report, it has six years to audit you. And if you didn’t file a return or the IRS claims that your return was fraudulent, there is no audit deadline; you’re always fair game.
Based on these rules, some experts advise that you simply give up and keep all of your tax records forever. There's no harm in keeping all of your actual tax returns forever; they don’t take up much space and can help you track the financial life of your business over time. You can generally get rid of supporting documents six years after you file your tax returns. They are only required if there is evidence you filed a fraudulent return.