There are no differences in the steps for approving and rejecting expense forms when you are a member of an approver/auditor group. You should, however, be aware that all members of your approver/auditor group have the same approval authority that you do. It takes only one signature from a member of your group to fulfill the group's approval requirement. As a result, you cannot approve an expense form if another approver/auditor in your group has already approved it. You can, however, reject a form that has been approved by a member of your group.
If you try to approve an expense form that has already been approved by a member of your approver/auditor group, an error message appears.