The statute of limitations for saving Federal returns is generally three years after the date the return is filed. Returns filed before April 15th are considered filed on the due date of the return or April 15th.
The IRS How long should I keep records? webpage explains:
The length of time you should keep a document depends on the action, expense, or event which the document records. Generally, you must keep your records that support an item of income, deduction or credit shown on your tax return until the period of limitations for that tax 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 the IRS can assess additional tax. The information below reflects the periods of limitations that apply to income tax returns. Unless otherwise stated, 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.
Note. Keep copies of your filed tax returns. They help in preparing future tax returns and making computations if you file an amended return.
The following questions should be applied to each record as you decide whether to keep a document or throw it away:
Generally keep records relating to property until the period of limitations expires for the year in which you dispose of the property. 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.
If you received property in a nontaxable exchange, your basis in that property is the same as the basis of the property you gave up, increased by any money you paid. 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.
When your records are no longer needed for tax purposes, do not discard them until you check to see if you have to keep them longer for other purposes. For example, your insurance company or creditors may require you to keep them longer than the IRS does.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.