(1) Contracts shall provide that delivery payments shall be made only for completed supplies and services accepted by the Government in accordance with the terms of the contract. Contracts may provide for commercial advance and commercial interim payments based upon a wide variety of bases, including (but not limited to) achievement or occurrence of specified events, the passage of time, or specified times prior to the delivery date(s). The basis for payment must be objectively determinable. The clause written by the contracting officer shall specify, to the extent access is necessary, the information and/or facilities to which the Government shall have access for the purpose of verifying the contractor’s entitlement to payment of contract financing.