Keep records for 3 years if situations (4), (5), and (6) below do not apply to you.
Keep records for 3 years from the date you filed your original return or 2 years from the date you paid the tax, whichever is later, if you file a claim for credit or refund after you file your return.
Keep records for 7 years if you file a claim for a loss from worthless securities or bad debt deduction.
Keep records for 6 years if you do not report income that you should report, and it is more than 25% of the gross income shown on your return.
Keep records indefinitely if you do not file a return.
Keep records indefinitely if you file a fraudulent return.