Remove the user's permissions:
- Go to Administration > Set up system security
- Open the user account
- Remove the groups selected in the "member of" box
- Click OK to the following message: "This user has not been given any group rights. The user must be a member of at least one group before they will have access to the system."
- Click Save and Close on the user account
- Now when the user tries to login, they will receive the following message: "The system administrator has not given you security rights to access The Financial Edge system."