Русско-англо-русский юридический словарь

Once you agree on a price, make sure to split the payments in such a way that the final payment (a substantial portion of the total amount) will be made only when the work has been fully completed and you have signed off on it. (Forbes)

An OTC or over-the-counter transaction, facilitates trades between two parties more privately, with one party acting as a “desk” (the business involved in buying and selling a particular form of an asset). The two parties agree on a price and then work out the transfer of assets between themselves. (Business 2 Community)