Stop Microsoft Bookings booking over Outlook events

The main Microsoft Q&A thread on this (2020) has 257 "same question" votes. Its accepted answer is this per-staff setting.

Turn on calendar sync for each staff member#

1. Open Bookings → Shared booking pages → your page → Staff.
2. Edit the staff member.
3. Tick Events on Microsoft 365 calendar affect availability. Microsoft's docs also call it "Events on calendar affect availability" or "Events on Office 365 calendar affect availability". It's the same setting.
4. Save. Repeat for each person, and on every booking page they belong to.

It's on by default for new staff, and Microsoft strongly recommends leaving it on to avoid double bookings. With it on, a 3pm team meeting makes that person unbookable at 3pm.

Make sure Bookings can read their free/busy#

If Bookings shows "This staff member's calendar can't be synced", or seems to ignore someone's meetings, that person needs to share free/busy. Microsoft's steps:

1. In Outlook on the web, select Share → Calendar.
2. Under People inside your organization, set My Organization to Can view when I'm busy.
3. Select Done.

This shares free/busy only, not subjects or details.

Two more account-level blockers:

• External staff (added with an email from outside your tenant) can't share free/busy at all. Bookings only knows about their Bookings appointments. See external staff.
• If your admin turned on Require staff approvals before sharing free/busy information (admin center → Settings → Org settings → Bookings), each person has to approve the request email before their availability is shared.

Events that still don't block#

Subscribed and secondary calendars#

Only the default Exchange calendar counts. A 2023 thread with 37 "same question" votes asked why subscribed calendars were ignored. The answer was that Bookings is designed to use the Microsoft 365 default calendar for free/busy, and subscribed or holiday calendars aren't included. The same goes for extra calendars created in Outlook and for Google or iCloud calendars (see Google Calendar). To make that time count, add Busy events to the primary calendar.

All-day events#

Outlook all-day events default to Free, so Bookings treats the day as open. A 2026 thread about a staff member bookable during all-day events came down to this. Set the event's Show as to Busy or Out of office. For planned leave, Add time off in the Bookings Calendar is more reliable (see holidays and time off).

Events marked Free#

Anything shown as Free doesn't block, including meetings accepted as Free and focus time that someone set to Free.

"Anyone" services with several staff#

If a service has several staff and the customer chooses "Anyone", the slot stays open while at least one assigned person is free. A 2025 thread where the owner was Busy but still got booked came down to this. Also check the service is set to Bookable when staff are free under Availability options.

Group services#

If Maximum attendees per event is above 1, the service is a group service. Several people can book the same slot on purpose. Set it to 1 for 1:1 appointments. See group bookings.

Double-booking across two booking pages#

Several threads (2021, 2024) report the same person being double-booked by two separate booking pages, even with calendar sync on for both. For example, one German and one French page with the same staff. A new Bookings appointment is written to the staff member's calendar, so the other page should see it as Busy. Users reproduced the double booking anyway, and neither thread has a Microsoft fix.

To reduce the risk:

• Put the services on one booking page where possible, and use per-service links to send people to the right service. See direct links to a service.
• If you must use two pages, check both calendars for overlaps daily and move one of the clashing appointments quickly.

Changes not showing yet#

Availability is recalculated when the page loads and again when someone books. Microsoft says transient sync errors usually clear within a few minutes. If a new Outlook event still isn't blocking after that, reload the booking page. If it keeps happening, see no available times for the opposite problem and the fuller checklist.