42 CFR § 408.207 - Billing and payment procedures.
(a) Adding and removing enrollees. The State or local government agency must transmit an input file containing addition and removal records electronically to CMS as follows:
(1) Input files must be transmitted at least once each calendar month, but may be transmitted as often as once a day.
(2) CMS will not add or remove enrollees retroactively, except for removals upon the death of an enrollee.
(3) The State or local government agency must pay the SMI premium surcharge for each eligible enrollee who is included in the agreement for the time period beginning with the month the enrollee is added and continuing through the month the State or local government agency informs CMS that the enrollee is to be removed, the month the enrollee's Part B coverage terminates, or the month of the enrollee's death, whichever comes first.
(b) Payment and grace period. Payment must be made to CMS as follows:
(1) Payment to CMS must be received by CMS by the first day of each month.
(2) There is a 10-day grace period for receipt of payment.
(3) Payment must be made to CMS via electronic funds transfer.
(c) Late payment penalties. CMS may assess interest for any payment it does not receive by the first day of the month as follows:
(1) Interest will be assessed at the SMI trust fund rate as computed for new investments in accordance with section 1841(c) of the Act.
(2) Interest will be waived if the full payment is received by the 10th day of the month in which it is due.
(3) Interest will be calculated and assessed in 30-day increments.
(4) Interest will be assessed on the balance of the amount billed that remains unpaid at the expiration of the grace period and unpaid balances from prior periods.
(5) Interest will continue to accrue on unpaid amounts until the balance is paid in full.
(d) Disagreement over billing amounts or interest. If the State or local government agency disagrees with the amount assessed in a billing statement or interest charge, it must notify CMS as follows:
(1) The State or local government agency must provide evidence suitable to CMS to substantiate its claim.
(2) The State or local government agency must continue to make full payment while CMS evaluates the evidence provided.
(3) Credit for payment amounts or interest that CMS determines to be due to the State or local government agency will be reflected as an adjustment in subsequent bills, effective on the date the corrected amount would have been due.