I'm here to share some information about adding business logos in QuickBooks Online.
Currently, we can only add one logo to sales form templates in QBO. As a workaround, you'll want to consider adding the two logos in one image or file. Then, upload it into the program. Here's how:
Click the Gear icon at the top.
Choose Custom Form Styles under Your Company.
Locate your template, then select Edit under the Action column.
Go to the Design tab, then click Add your unique logo.
Select the Add a logo box, then find and select the edited image.
Click Open and select Save, then Done.
I've also attached some articles that will help you personalize the invoices, estimates, and sales receipts that you send to your customers: