_Payment in arrears_ is a payment made after a service has been provided, as distinct from _payment in advance_, which are payments made at the start of a period.

A _payment in arrears_ has occurred when a payment is made to a supplier later than the terms of the arrangement under which goods or services were to be purchased from the supplier.

Спасибо. Оба варианта правильные, кажется

Вам стоит добавить свой вариант как перевод.