The amount of GST you collect may change at times, @tekautopl. You will, however, have to change it manually. 

I'll walk you through the steps to update it:

1. Go to Taxes menu, then select Edit rates in the Edit GST dropdown menu.
2. In the tax rate table, choose the rate you want to change and select Edit.
3. In the Edit tax rate window, change the rate to 7%. 
4. Set the Effective date.
5. Select Save, then click Yes.

You'll want to check out this article for the step-by-step guide in applying and managing credit notes in QBO.

I'll be around to help you again with your tax rates concerns. Take care!