6c37871c__11_CCP_Installment_Agreements__If_the_reason_box_states_
[And ...] the account has a -C freeze [Then ...] If two payments have been missed, close case. Note: Do not send 2975 default letter. Provide updated information to IAT administrator. [If the reason box states:] 
Combat Zone and Military Deferment
Internal Revenue Manual - 5.4.11 CCP Installment Agreements