It is a standard contractual provision, unless otherwise amended by the parties of the contract that the UN is obligated to pay for goods or services net 30 days upon the vendor's satisfactory completion of its delivery obligations in accordance with the delivery terms.

In addition, when normal commercial practice or the
interest of the UN so require, advance or progress payments may be agreed upon in accordance with Financial Rule 105.19(a) and 105.19(b). The Procurement Officer/Assistant shall record the reasons for advance or progress payments in the procurement case file.

Payment on Partial Delivery of Goods/Services
Under certain conditions, the UN may agree to pay for partial delivery of the goods or upon completion of clearly defined milestones for services or works, provided adequate security for the advance or progress payment is established. In such cases, the Procurement Staff should consider establishing specially developed payment terms. Provided such terms are approved by the Director, UN/PD or the CPO, they should consider payment flows and tailored to the specific procurement.