Not invoices, just cash transactions need receipts. The receipts are issued by machines that can sync with the government services frequently, but it's not syn

Not invoices, just cash transactions need receipts. The receipts are issued by machines that can sync with the government services frequently, but it's not synchronous. All transactions are written in a special "flash" memory and synced via the included data sim card each 5-10 minutes. Buffering up to 24 hours is possible.