42 CFR § 408.62
Initial and subsequent billings
June 11, 2020
(a) Monthly billing.
(1) The first premium bill is for the period from the first month of coverage (or the first month of change from deduction or State buy-in payment) through the end of the first month after the month of billing.
(2) Subsequent billings are for periods of one month.
(b) Quarterly billing.
(1) The first premium bill is for the period from the first month of coverage (or of change from deduction or State buy-in payment) through the third month after the month of billing.
(2) Subsequent billings are for periods of three months.