How do you change the invoice template so it appears the same on new and old invoices?

Hi there, @Kdrum1. 

Thank you for reaching out to the community. 

Let me walk you through on how to invoice template and customize it smoothly.  

Here's how: 

1. On the left pane click Sales and choose Invoices. 
2. Select the specific invoice you want to customize, the under Action drop-down arrow choose View/Edit. 
3. Click Customize either New style or Edit current. 
4. Go to the Design tab to edit the template name, logo, color, font, and margins. 
5. Go to the Content tab to customize the header, body, and footer of the invoice template. 
6. Hit Done.

Here's the link for your reference: Customize your invoices, estimates, and sales receipts in QuickBooks Online. 

Let me know if you need anything else about this. I'm just a one post away. Have a great day!