The same-day booking, written that morning
A same-day booking is one requested for later the same day; for a returning guest, one or two hours at a city address is then paid entirely at the door.
A same-day booking is exactly what it sounds like: written on the day it happens, for an hour later that day. On a long stay it becomes the usual way to book for many guests, because it lets the decision wait until the evening is certain.
What makes it different
It is the only kind of booking that can be paid entirely at the door. That applies when three things are all true: the guest has booked with the house before, the booking is for one or two hours, and the address is in the city. Change any one of them with a first booking, three hours or Schiphol, or add a peak date or a second therapist, and half goes ahead as usual.
The trade-off
Choice narrows on busy evenings. A same-day request asking for a particular therapist may find her already booked. The reply says who is free at the hour you asked for, and the choice from there is yours.
A first booking on the same day
That works too, with a deposit because it is a first booking, and with one extra line: you confirm in the thread that you want the session performed at once. The reason is explained on the booking terms page.
Cancelling one
With no deposit behind it, a same-day booking costs nothing if called off before she sets out, and only the journey share after.