There is no IRS deadline for overdue previous year tax returns, but in order to claim a tax refund for a certain year, you must file a tax return for that year within 3 years of the original due date. If you wait longer than 3 years, any tax refund is forfeit.
On the other hand, past due taxes do not disappear. If you owe taxes for a previous tax year, the IRS may charge you。
从网上取的(deadline for tax return 2011),可能不对。