When an expense in a submitted report needs to be amended, you can amend the expense and approve the report after amending it.
When opening the report, you can click on the expense, there you can amend the expense as needed, like your normal expenses. You can f.e. change the amount when this is not in line with company policy or change the category when the wrong category is chosen.
When the amount is changed this will show in Declaree, and this will show in the report history.
After this you can approve the report as you are used to.