If you attempt to delete a posted write-off whose date is in a previous period, you get the error "Data could not be saved. Post date must be in an open period." I would think that the process should use the current date as the posted data for the write-off reversal, but it is attempting to use the date of the write-off. When making any adjustment, that adjustment posted date is the date it occurred. You would NOT want to go back and have a change made to your GL for a previous closed period. This would not be approved by auditors or the IRS.