Why can’t I make changes to a reimbursed report?

Recording the reimbursement is the last action related to a report. The accounting entries for your expenses will be made by your finance team before making the reimbursements. Once the reimbursement is done and accounted for, no changes can be made to the report as it will cause mismatch with the reimbursement transaction made in accounting. Hence, if you need to make any changes to the report, you will have to 'Undo Reimbursement' for the report.