IRS Notice Decoder Enter the notice number shown on your IRS letter to learn what it means and the next steps you should take. Search Result Common IRS Business Notices CP14 CP90 CP136 CP161 CP207 CP259 CP276B CP297 CP501 CP503 CP504 CP518B Letter 226-J Letter 903 Letter 1058 (LT 11) Letter 1153 Letter 2030 Letter 2800C Letter 3172 Letter 5005-A