The IRS technically can require you to file late, or delinquent, tax returns as far back as they want. There is no statute of limitations. In practice, the IRS rarely requires people to file tax returns that are more than six years overdue. Also, they typically complete delinquent-return enforcement actions within three years of the original due date of the return. When you have unfiled returns, the IRS can assess both failure-to-file and failure-to-pay penalties, and charges interest on any money you owe them. In most cases, the IRS must forgive unpaid taxes, penalties, and interest after 10 years of non-payment, starting from when the tax return was filed, or the tax was assessed. During those 10 years, you are at risk of tax liens, tax levies, difficulty qualifying for loans, and even having your passport revoked.