A late arrival is a client who turns up after the time they were booked for. Five minutes is usually absorbed. Twenty minutes into a 45-minute service is a different problem: either the service is cut short, the clients after them are kept waiting, or the appointment has to move. A late arrival policy decides in advance which of those happens, so the call is not made on the spot by whoever is at the desk.
The simplest policies set a grace period and say what happens after it. For example: up to 10 minutes late, the full service if the diary allows; more than 10 minutes, a shortened service at the usual price, or a new booking with the cancellation rule applied.
In practice
A brow bar books 30-minute appointments back to back. A client arrives 12 minutes late for a $65 shape and tint. Doing the full service would make the next three clients wait 12 minutes each. The bar's own rule is that after 10 minutes the tint is left out and the client pays for the shape alone, $40, or moves to a new time. She chooses a new time. With a 10-minute buffer after each appointment, the bar could have absorbed most of the delay and done both services.
Say the rule before it is needed: in the confirmation text, on the booking page and at the desk. And treat a client who rings ahead to say they are running late differently from one who simply appears, because the call gave you time to rearrange.
In Glow Line
A client who rings to say they are running late while you are with someone reaches the assistant, which takes a message. The text arrives on your mobile with the summary and the number, so you can glance at it between steps and decide. See call summaries.