It is important to know that all accepted Offers of Appointment are considered part of an applicant's history and can be seen TAs' and SLs' Profile -> Offer History.
There may be exceptional circumstances when one or more of the following (minor) details change AFTER an offer has been extended and accepted:
Once the TA or SL has agreed to the change(s), in writing (via email):
NOTE: No other details of an accepted offer can be edited without Withdrawing the Offer and Creating a New Offer.