I just realized that I must file U.S. income tax returns for prior years. How many years back do I have to file?

You must file a federal income tax return for any tax year in which you meet the filing requirements to file a tax return. For most taxpayers, if your gross income is equal to or greater than the personal exemption amount and standard deduction combined (per the Form 1040 Instructions for the corresponding tax year), a tax return must be filed. There is no statute of limitations for unfiled tax returns. Thus, the recommended number of prior years to file will depend on the facts and circumstances of your particular situation, which should be discussed with your tax professional.