Final answer:
A taxpayer may not file an amended return if they are outside the statutory limit to claim a refund, which is typically three years from when the original return was filed or two years from the payment of the tax, or if the IRS has begun a proceedings to issue a Notice of Deficiency, or after accepting an offer in compromise.
Step-by-step explanation:
A taxpayer may NOT file an amended return after the due date of the original return if they are outside the statutory limit for claiming a refund, which, according to the Internal Revenue Service (IRS), is generally three years from the date the original return was filed or two years from the date the tax was paid, whichever is later. There are also other specific circumstances under which amending may not be permissible, such as if the IRS has commenced a proceeding to decide whether to issue a Notice of Deficiency (NOD), during which time a taxpayer cannot amend a return. Another example is when a taxpayer has elected to waive the right to file an amended return by choosing the IRS's offer in compromise.