thank you for the response, I finally contacted the IRS.
the CP04 was for 2020. we have already filed and paid all tax due for 2020. The IRS however told me that we have to file the 15109 "request for tax deferment" even if we don't want to request tax deferment. that seems counter-intuitive to me still (why do they call that a request for tax deferment if we are not requesting it). they basically need to have the dates for the combat pay.
thanks again
