November 14, 2019 The CP2100 and CP2100A Notices have a new look. The redesigned notices provide more information to payers who file certain information returns about: types of taxpayer identification numbers issued which "B" notice to use how and when to send "B" notices how to validate TINs when to stop backup withholding what to do after receiving a notice IRS sends out CP2100 and 2100A Notices twice a year, in October and the following April. The notices let payers know they may be responsible for backup withholding when TINs are missing from IRS records or have incorrect name/TIN combinations. The notice will list payees identified as having TIN issues. The payers should compare the notice with their account records and take appropriate action. More information is in Publication 1281 .