Hi @Welcome2018,

You can set a default footer message for invoices in QuickBooks Online (QBO), so you no longer need to enter it manually.

Let me show you how:

1. Go to the Gear icon.
2. Select Account and settings.
3. Click the Sales tab.
4. Tap the Messages section.
5. Change the default message in the Email message box if you want.
6. Under Sales form, choose Invoices and other sales forms. You can then type in the notes you want to appear on the footer. 
7. Hit Save, then Done.

You have the option to create and upload custom form styles in QBO. Take a look at this article for the steps: Import custom form styles for invoices or estimates. 

Tag me in a comment below if you have other questions about sales forms in QBO. I'll get back to you as soon as I can.