In principle, the first (advance) payment and the final payment are fixed. The remaining payments can be proposed by the Tenderer with respect to dates and amounts, but should take into account a balance between expenditures and payments and should be related to achievements (conclusion of work packages, development of hardware/software, reviews, etc).

Payment milestones have to be invoiced when reaching the achievements related to the specific milestones and as defined in the Milestone Payment Plan included in the contract. Each payment milestone is broken down to the amounts that pertain to each member of the Project team. Project Team members have to issue a specific invoice for the part of their competence. Subcontractors have to submit their invoices to the Prime contractor. The Prime contractor approves the invoices and submits them to ESA as specified in the contract.

External services cover services such as hire of facilities, computer services, manpower services (e.g. consultancy), plating of parts, services for procurement of HIREL parts etc. The costs for these should be shown on the PSS A2 form of the Prime Contractor under Other Cost Elements Point 3.7 and further detailed on Exhibit.