noun
settlement day; account settlement day
Refers to the day on which financial accounts are settled, such as in business transactions or at a store.
今日は勘定日なので、支払いを済ませなければならない。
Today is settlement day, so I have to complete the payment.
Compound of 勘定 (かんじょう, 'calculation, bill, account') and 日 (び, 'day'). The reading び is a rendaku form of ひ.