The length of time you should keep a document depends on the action, expense, or event the document records. Generally, you must keep your records that support an item of income or deductions on a tax return until the period of limitations for that return runs out.

The period of limitations is the period of time in which you can amend your tax return to claim a credit or refund, or that the IRS can assess additional tax. The below information contains the periods of limitations that apply to income tax returns. The years refer to the period after the return was filed. Returns filed before the due date are treated as filed on the due date.

Generally Keep Records for Three Years (Four Years for California)
Federal law generally requires you to maintain copies of your tax returns and supporting documents for three years.

California law generally requires you to maintain copies of your tax returns and supporting documents for four years.

We recommend you retain your records for seven years for both Federal and California purposes.

Records Connected to Assets
Keep records relating to property until the period of limitations expires for the year in which you dispose of the property in a taxable disposition. You must keep these records to figure any depreciation, amortization, or depletion deduction and to figure the gain or loss when you sell or otherwise dispose of the property.

Generally, if property is received in a nontaxable exchange, you must keep the records on the old property, as well as on the new property, until the period of limitations expires for the year in which you dispose of the new property in a taxable disposition.