Is there a way to add a co-owner to the Quickbooks app so they can upload receipts?

I'm glad to help you with that, support-sweetsav. 

In the QuickBooks app, there's no option to add a user. However, if you want to add a user for them to upload a receipt, you can add it through a web browser or your QuickBooks Online account. Here's how:

1. Click the Gear icon ⚙ and select Manage users.
2. On the Users tab, press Add user.
3. Select the Roles ▼ dropdown, then choose the role you want to assign to the user.
4. Select the Account management settings you want to manage (only if applicable).
5. Hit Send invitation.

New users will receive an invite to join the company. Let them select the Let's go! link in the email for them to create a new Intuit Account or sign in if they already have one.

On the other hand, if you wanted to add a co-owner as a partner to your company. I've added an article with detailed steps to create a co-owner profile.

• Add an owner or partner to your books in QuickBooks Online
• Record an owner's contribution or capital investment in your business

In addition, you can check this article for you to learn how to add a vendor in QBO: Add a vendor in QuickBooks Online.

Comment down below if you have further questions on adding a co-owner. I'll be right here to help.