Generally, all income taxes must be assessed within three years after the original return is filed (the last day prescribed by law for filing if the return was filed before the last day) ( Code Sec. 6501; Reg. §301.6501(a)-1). 51 In the case of pass-through entities, the three-year rule begins to run at the time the pass-through entity’s shareholder or other beneficial owner files an individual income tax return. A return filed prior to its due date is deemed to have been filed on the due date. A return executed by an IRS official or employee in which the taxpayer has not filed a return will not start the running of the statute of limitations. A proceeding in court without assessment for collection of the tax must commence within the same period. The period can be extended by a written agreement between the taxpayer and the IRS ( Code Sec. 6501(c)(4); Reg. §301.6501(c)-1(d)). 52 Interest on any tax may be assessed and collected at any time during the period within which the tax itself may be collected ( Code Sec. 6601(g); Reg. §301.6601-1(f)). 53

If, within the 60-day period ending on the last day of the assessment period, the IRS receives an amended return or written document from the taxpayer showing that additional tax is due for the year in question, the period in which to assess such additional tax is extended for 60 days after the day on which the IRS receives the amended return or written document ( Code Sec. 6501(c)(7)). 54

If unused foreign tax credits have been carried back, the statute of limitations on assessment and collection for the year to which the carryback is made will not close until one year after the expiration of the period within which a deficiency may be assessed for the year from which the carryback was made ( Code Sec. 6501(i); Reg. §301.6501(i)-1). 55 Deficiencies attributable to carryback of a net operating loss, a capital loss, or the general business and research credit, may be assessed within the period that applies to the loss or credit year. Deficiencies attributable to the carrying back of one of those credits as a result of the carryback of another credit, a net operating loss or a capital loss, may be assessed within the period that applies to the loss or other credit year ( Code Sec. 6501(h) and (j)).