To claim a refund, you must file an amended return within 3 years after the date you filed your original return or 2 years after the date you paid the tax. Many find the easiest way to figure the entries for Form.X is to first make the changes in the margin of the return they are amending. To amend a previously filed Form TPT‑2, check the. "AMENDED RETURN" box under TAXPAYER INFORMATION section. You can amend your return at any time, but to claim a refund, the amended return must be filed within three years from the original due date of the return.