Procurement documents has only 2 parties (Supplier & Buyer), how to include the (Beneficiary)?

Nice day All,

Is there standard field to mention 3 parties in procurement documents (PO/RFQ) for (Sub-Contractor) type?

Business Case;

- Our client is offering tender and supervision and implementation phases to calculate a beneficiary

- After selecting a supplier who has been awarded the tender by the contract is signed by 3 parties’

    # Authority supervising the implementation of the tender and the contract
    # the beneficiary of the Tender
    # Supplier

Procurement documents has only 2 parties (Supplier & Buyer), how to include the (Beneficiary)?

Thank You

Magdy Ikladious