Deposit language that survives a delay
A deposit buys a calendar slot, and the wording has to say so.
What the deposit actually buys
The deposit is not a down payment on a deliverable; it is the price of holding a slot in your calendar. Once that distinction is in the agreement, a refund conversation becomes a scheduling conversation, which is much easier to have.
The start date is the cleared date
Projects begin when funds clear, not when the agreement is signed and not when the transfer is promised. Stating this in one sentence prevents the common pattern of a project that starts late but keeps its original deadline.
Refund position in one line
Say plainly that the reservation is not refundable once the calendar is held, and say what happens if the client postpones rather than cancels. Two lines cover almost every real case.
Do not call it a deposit if it is refundable
If the money can come back at any time, it is not a commitment and it should not be described as one. Choose the wording that matches the risk you are actually taking.