where a contribution is paid under an arrangement to which regulations F368 and 84 or, as the case may be, regulation F490 of the Contributions Regulations M1 (other methods of collection and recovery of earnings-related contributions; special provisions relating to primary Class 1 contributions and arrangements approved by the Inland Revenue for method of, and time for, payment of Class 2 and Class 3 contributions respectively) apply, the date by which, but for the said regulations 4 to F17A and F261, the contribution would have fallen due to be paid shall, in relation to that contribution, be the due date;

any payment made of, or as on account of, a contribution in accordance with any such arrangement shall, on and after the due date, be treated as a contribution paid on the due date.