An Advance Checked In reservation can be modified under these conditions:
When a reservation is Advance Checked In, the arrival date is changed to read-only and cannot be modified.
You can assign, remove, or modify a room on an Advance Checked In reservation.
It can be reversed unless financial transactions exist on the folio. Reservations with deposits are eligible to be reversed.
It cannot be moved to another property.
It cannot be canceled. First, you must reverse the advance checked in flag and then you can cancel the reservation.