The balance on arrival is whatever the deposit left unpaid, handed over once she is inside, in banknotes of any major currency, by card, or in crypto.
A booking's fee arrives in at most two parts. The first, where a booking carries one, is the deposit, settled electronically before she sets out. The second is the balance, paid when she arrives and before the session begins. Settling at the outset means the time that follows contains no transaction at all.
Half the fee, which is the ordinary case. A first booking of two hours costs EUR 360; EUR 180 went ahead, and EUR 180 is the balance.
The whole fee, which is the exception. A returning client asks for one or two hours today, nothing is sent in advance, and the full EUR 180 or EUR 360 becomes the balance.
A figure already reduced by credit. Where force majeure was accepted on an earlier booking, that credit counts as paid, and the balance on the later booking falls by the same amount.
Banknotes are accepted in euros and in other major currencies, which are converted at that day's rate, so pounds, dollars or francs carried from home need no exchange first. Card works. Crypto is accepted as well. The method need not match the deposit's: an advance sent through Wise can be followed by a balance in banknotes.
The balance is written in the thread at confirmation, beside the deposit where one applies, so there is nothing to calculate at the door. Amounts on the price page are full fees; halve one to find the ordinary balance. The FAQ answers questions about currencies and cards.