Should I charge for sessions when a client doesn't turn up or cancels with short notice?

I’m afraid that the experience of many private practitioners is that clients sometimes don’t turn up or don’t give 24 hours’ notice of any cancellation. A rough guesstimate from looking back over my diary and from talking informally to private practitioner friends would suggest that this happens between ten and twenty per cent of the time. If you have a twenty-session week booked, you could expect at least four of those appointments not to happen.