Keeping accurate paper records is important for identifying sources of income, expenses, property records and completed tax returns. You should keep these paper records in case you’re audited. But how long? The answer is: it depends.

According to Table 3, Period of Limitations from IRS Publication 552:

1. IF you… Owe additional tax and (2), (3), and (4) do not apply to you: 3 years

2. IF you… Do not report income that you should and it is more than 25% of the gross income shown on your return: 6 years

3. IF you… File a fraudulent return: No time limit

4. IF you… Do not file a tax return: No time limit

5. IF you… File a claim for credit or refund after you filed your return:  The later of 3 years or 2 years after tax was paid.

6. IF you… File a claim for a loss from worthless securities: 7 years

Source: http://www.irs.gov/publications/p552/ar02.html