On Cloud, you can see the outstanding balance for a project in two places.
In the Project Details view, under the Payments tab.
Check out this article for more details.
On the project tile on the Projects page, in the Kanban view. To see the outstanding balance in the Kanban view, you will need to set the "Balance Value Display" toggle to ON, under "Settings > Project > Project Stages," and click the Outstanding Balance option below it. Now, you will see the outstanding balance on the project tile and on the header of the project stage.
Here is a screenshot of the setting enabled and the Outstanding Balance option selected.
If you select the Total Outstanding option, you will see the Total Outstanding value on the tiles and on the header of the project stage.
You will need to be part of built-in Administrator group to enable the setting.