Group services and attendee limits in Microsoft Bookings

A group service is an ordinary Bookings service with Maximum attendees per event set above 1: one time slot with the same staff member stays bookable until that many customers have taken it. You have to decide this when you create the service, because Microsoft locks the service type once it's saved. That lock is why the field is greyed out on existing services. Step-by-step setup is in group bookings and classes; this chapter is the reference for how capacity behaves and where the limits are.

Service types and their names#

Microsoft's own articles name these differently, so it helps to map them to the settings you actually see.

Inconsistencies to know about, as of October 2026:

• The service article calls the field Maximum attendees per event. The service-types and attendee articles call it Maximum number of attendees. A 2026 Q&A poster saw it as "available number of seats". It's the same setting (maximumAttendeesCount in Graph).
• The service article calls the staff option Multiple staff and names it N:1. The service-types article calls it Assign all of your selected staff for an appointment, and its introduction labels 1:N "personalized" and N:N "group".

Why the field is greyed out#

The service-types article says that once maximum attendees is set, "the service type (multi customer or single) can't be edited further". A service saved as 1:1 can't become a class, and a class can't go back to 1:1. The fix is always a new service:

1. Create the new service with the right maximum.
2. Switch the old service's Publishing options to Off. Hiding it doesn't delete it or its bookings.
3. Share the new service's own link. See direct links to a service.

A separate trap: Microsoft says editing a group service from the Teams app or the mobile app resets attendees to 1. Edit group services only in the Bookings web app, and recheck the value if someone has touched the service elsewhere.

How capacity is counted#

• Per service, staff member and start time. Microsoft describes the slot "for the selected service, staff, and time" staying open until the maximum is reached. Two instructors on a 1:N service are two separate sessions, each with its own capacity.
• Customers, not guests. Graph counts filledAttendeesCount as "the current number of customers in the appointment". Microsoft doesn't document whether extra guest email addresses count against capacity, and we haven't tested it.
• One appointment per session. Every customer is added to the same appointment, so the staff calendar shows one event with all of them. The 2026 Q&A thread above describes exactly that: one meeting with two customers and four staff.
• Outlook doesn't stop the second customer. Once a session has one customer, the time is busy on the staff calendar, but the group slot stays open on purpose. The Microsoft moderator on that thread put it plainly: "Outlook free/busy alone does not prevent this when the service capacity is greater than 1". If a 1:1 service is double-booked, check this field first.
• Random staff choice can split a session. When a customer picks "Anyone", Bookings assigns a free staff member at random (FAQ). With several instructors on one 1:N service, attendees can spread across instructors instead of filling one session. Assign one instructor per service if you need one full room.
• API bookings need customer records. Graph says that for services with a maximum above 1, you must pass valid customer IDs when creating or updating an appointment.

What customers see#

A group session looks like any other time on the page: the customer picks it, fills in the form and gets their own confirmation. When the session is full, the time disappears. Microsoft doesn't document a "places left" count on the booking page, and we haven't verified whether one is shown. Each attendee manages their own booking from their confirmation email.

Microsoft lists a known problem where one attendee cancelling sends cancellation emails to all attendees. The documented mitigation is to untick Send a meeting invite to the customer, in addition to the confirmation email on the service's Notifications tab.

Managing attendees#

Open the session in the Calendar and select Edit. Add customer adds someone. Select a person and Remove customer to take them off; they get an email saying so. You need the Administrator or Team member role. The Calendar also shows each session's current capacity. For a list you can use outside Bookings, see exporting customers.

Limits as of October 2026#

What we saw when testing (September 2026)#

One of our 13 captures of the public booking page was a group service with a capacity of 5 (1-hour lead time, 30 days in advance), and the page's slots matched our reproduction exactly. In the page code, a partly filled session comes back from the server marked "slots available" and produces exactly one slot, at the session's start, with no buffer adjustment. We read that from the code; our captures had no partly filled session, so we haven't seen it live.

For classes in schools and universities, the education guide covers term dates and student-only access alongside group sessions.

BookingsXP is independent and not affiliated with or endorsed by Microsoft.