quantum meruit
/ˈmerʊɪt/noun
mass noun［usu. as modifier］
- Law a reasonable sum of money to be paid for services rendered or work done when the amount due is not stipulated in a legally enforceable contract【律】（无合同规定时）按服务计值; 按劳计酬。
词源
Latin， literally 'as much as he has deserved'.