Hi. Does anyone know how to change the margin size on invoices please?

Hello ap8,

Changing the margin size for sales forms in QuickBooks Online is simple. You can click on the Gear icon, choose Design tab, and click on Edit printer settings. Adjust the margins from there. 

You may also want to import your customize template. I'll share this article for you to see the steps: Import Custom Form Styles For Invoices or Estimates.

If you need anything else, please let us know. Thanks!