If all of our self employment income is reported on A T 4 do we need to report anything else if we're not claiming expenses?

If you have self-employment income on a T4, then you have to fill out a T2125 Statement of Business or Professional Activities, even if you have no expenses.

You only need to answer basic information, such as business name and address (can be your own), industry code, and fiscal period (Jan 01 to December 31).