Two customers turn up for the same appointment. Or someone misses theirs and says they never got a reminder, even though your system says it sent one.

It's an awkward moment, and it's rarely anyone's fault. Most booking problems come from a few ordinary gaps between the places bookings arrive.

This is a check you can do yourself in about fifteen minutes. You don't change anything. You only look.

Why double bookings happen

  • Bookings arrive in more than one place. Your website, the phone, a marketplace and a paper diary can each say a slot is free, because each only knows about its own bookings.
  • The booking tool isn't looking at the right calendar. It can only avoid clashes on the calendars it has been told to check.
  • An appointment is marked "Free". Calendars let you mark an event as Free or Busy, and many booking tools only treat Busy events as a clash.
  • Copies take time. When one system passes bookings to another, there can be a gap. Someone can book the same slot during that gap.
  • Times don't line up. If two systems use different time zones, a booking can land an hour away from where it belongs. This guide on time zones shows where to look.

The 15-minute check

1. List every way a booking can reach you

Write them all down: your website, phone, email, social media messages, marketplaces, walk-ins, and anything a member of staff keeps in their own diary.

Next to each one, write where the booking ends up, and who puts it there.

2. Ask one question about each route

When a customer books this way, does anything check the other routes first? If the answer is "someone remembers to look", write that down. That's the gap most double bookings come through.

3. See which calendars your booking tool checks

The setting has a different name in each tool:

  • Calendly: in Calendar settings, see which are ticked under "Calendars to check for conflicts". Calendly's guide to free and busy rules explains how it treats each event. It generally can't check calendars you've only subscribed to.
  • Google Calendar appointment schedules: each time on a booking page can only be booked once. Whether your other Busy events block times depends on the schedule's availability setting, and checking extra calendars needs an eligible plan.
  • Anything else: look in its settings for words like "calendar", "availability" or "conflicts".

4. Look at a week of appointments

Open a recent week in your calendar and click a few appointments. See whether each one shows as Busy or Free. Look hardest at anything added by hand, or copied in from another system.

All-day events are worth a look too, because a holiday can be marked Free and leave your booking page open.

Reminders that never arrived

Your tool saying a reminder was sent only tells you it left. It doesn't tell you the customer received it. Here's what often happens in between:

  • The phone number or email address has a small typo in it.
  • The email landed in a spam folder.
  • The customer booked by phone, so the reminder system never had their details.
  • The reminder automation stopped, or your plan ran out for the month.

To check, take one recent week and compare two counts: how many bookings you had, and how many reminders were sent. If your text message service shows a delivery status, look for anything other than "delivered".

Then look at the last no-show or two, and read the contact details on their booking. These guides cover the rest:

Habits that keep bookings in one place

  • One calendar is the real one. Every route ends up there, and anyone taking a booking by phone looks there first.
  • Read back the details. When someone books by phone, read their number and email address back to them.
  • Ask two questions after a no-show. Did the reminder go out, and were the details right? Over a few months, the answers show a pattern.

What to do with what you found

If every route checks the same calendar and your counts match, well done. Look again whenever you add a new way to book.

If you found a gap, your list of routes is exactly what whoever looks after your booking system needs to see.

And if there's nobody to ask, I can read through it for you, read-only. Here's an example of the findings note you'd get.