Balance on arrival names the remainder of a fee, settled with her on arrival in euros or other major banknotes, by card, or in crypto.
Most reservations on this site are paid in two instalments, and the second of them is the balance. It is settled with the woman you chose at the very start, once the door has closed behind her, so none of the booked time afterwards has money in it.
For the ordinary reservation the balance is exactly half. A first booking with Jasmin for one hour costs EUR 180; EUR 90 cleared as the deposit and EUR 90 is handed to Jasmin. A three-hour booking with Danielle costs EUR 540; EUR 270 went ahead and EUR 270 is paid to Danielle in the room.
For one kind of reservation the balance is the entire fee. A returning guest, asking for one or two hours with one woman on the same day, sends nothing beforehand and pays all of it on arrival, whether that sum is EUR 180, EUR 270 or EUR 360. That is the exception on this site rather than its habit, and as soon as a booking steps past those limits the deposit comes back into the picture.
Three methods, and any of them suits any booking. Cash in euros or another major currency, counted at the rate of the day; sterling, dollars or Swiss francs brought from home need no exchange counter first. A card. Or crypto. Cash settles the balance and only the balance; it never serves as a deposit, since a deposit must reach the office before she leaves. The two halves need not match, and a guest who sent the deposit by card may well hand over the balance in dollars.
The exact figure appears in the written confirmation, so nobody does sums on the doorstep. The first half is defined under deposit, the whole card is on the prices page, and questions about currencies are answered in the FAQ.