Refers to the written statement of charges, typically presented at the end of a meal or after a service.
Please bring the bill when we finish eating.
I'll pay after checking the bill.
勘定書 is typically used for an itemized bill at a restaurant or shop for immediate settlement, while 請求書 is the more general business term for a formal invoice sent for later payment.
Compound of 勘定 (かんじょう, 'calculation, bill') and 書 (しょ, 'document, writing').