Adding a logo to your customer's invoice is a breeze, @tc7shopfitterslt. I'd be happy to walk you through how to do that.
You can add your customer's logo on the invoice template by going to the Custom Form Styles section in QuickBooks.
Here's how you can achieve it:
For more tips about managing logos on your sales templates in QuickBooks Online, you can always check out this reference: Add, customise, or remove logos on sales forms.
Let me know if there's anything else that you need by leaving a reply below. I'll be more than happy to help. Have a nice day!