Returning client, and what the phrase really covers
A returning client is a guest whose earlier booking still shows in a live thread under the contact he writes from, proof that it was agreed and went ahead.
The phrase is used a great deal on this site, and it has a narrow meaning. A returning client is somebody the house has looked after before, and the only evidence of that is the written booking thread from an earlier visit. There is no membership, no card and no list of names kept anywhere else.
What it depends on
Two things. The thread must still exist, and it clears twelve months after its last message. And the new message has to arrive from the same number or address, or say clearly which old contact to look under. A guest who meets both is a returning client; a guest who meets neither is treated as writing for the first time.
What it changes
One thing only. A returning client asking on the day for one or two hours at an address in central Amsterdam pays the whole fee when she arrives. Every other booking follows the same deposit rules as anyone else's, and the rates are identical for all guests. The page for returning visitors covers the rest.