thirty day letter
thirty-day letter. A letter that accompanies a revenue agent’s report issued as a result of an Internal Revenue Service audit or the rejection of a taxpayer’s claim for refund and that outlines the taxpayer’s appeal procedure before the Internal Revenue Service. • If the taxpayer does not request any such procedure within the 30-day period, the IRS will issue a statutory notice of deficiency. — Also written 30-day letter. Cf. NINETY-DAY LETTER. [Cases: Internal Revenue 5044.]