How do I reverse an opportunity/payment so I can make changes to it?
Once a record has been exported to an external system, it's important that it's no longer edited in Salesforce. Sometimes mistakes happen a record needs to be corrected. Accounting systems often require that there is an audit trail of exactly what was changed and a separate journal entry transaction of the change. Here is how you would allow for that in Salesforce.
Reversing Records One at a Time
The Reverse button is gone and the record shows that the gift is reversed. It is now fully editable by any user.
Reversing Opportunities in Bulk
You can reverse up to 200 records at a time following the same idea as when they were posted.
Since Reversing only works on gifts that have been posted, make sure you are using a report that shows already posted transactions.