url=’http://legalbearsblog.com/2009/02/does-the-irs-screw-up-on-their-statutory-notice-of-deficiency/’; IRM 25.6.5.7.2 (03-01-2006) Statutory Notice of Deficiency (90 Day Letter) 1. A statutory notice of deficiency may be issued by Examination, Collection, Deferred Adverse Tax Consequence (DATC/ASTA) and the Document Matching functions. Except for certain limited exceptions, a statutory notice of deficiency must be issued to assess and collect an income tax, estate tax, [...]