The event went great and the client wants to leave a tip for your team. They can do this even if the booking is already paid in full.
Send a tip link
Bookings → Select booking → Make Payment
Open the booking.
Click Make Payment.
Scroll to the bottom of the page and copy the link.
Send the link to your client. They can add a tip without logging in.
Tips show up in the Tips report. To set up tips, suggested amounts, or a tip field during initial booking, see how do I let clients leave a tip.