It's not necessary to use cash register with Invoicebox system. In accordance with 54-FZ, the receipt must be issued / processed at the time of calculation. Since Invoicebox system is authorized to receive payments for goods and services, the moment of payment with the custoumer comes from Invoicebox system. Respectively, the obligation to issue fiscal receipts arises in Invoicebox system. Fiscal receipts are stored by the Invoicebox system on its own cash registers.
