To edit an expense, it should not be in submitted, approved, controlled or reported status. If you have submitted an expense and you want to edit it again, you can recall it for editing (if the expense is still in the "submitted" status).
Steps to edit expense.
1. In the Expense section, under your TO DO, select the expense you would like to edit.
2. You can double click on the selected expense, then edit the necessary fields.
Or you can select the checkbox next to the expense, click Action and select Edit
Once done, click Submit or Save.