There shall be a provision as follows:

TIME OF PAYMENT OF CLAIMS: Indemnities payable under this policy for any loss other than loss for which this policy provides any periodic payment will be paid immediately upon receipt of due written proof of such loss. Subject to due written proof of loss, all accrued indemnities for loss for which this policy provides periodic payment will be paid . . . . . . (insert period for payment which must not be less frequently than monthly) and any balance remaining unpaid upon the termination of liability will be paid immediately upon receipt of due written proof.