Adding QR codes on invoices is currently unavailable in QuickBooks Online. You may want to look for a third-party application to integrate with QuickBooks that supports this feature.
You can visit our QuickBooks App Center to check for an application that can help you add QR code to your invoice.
Here's how to do it:
From the left menu, select Apps.
To find apps, select the Find Apps tab.
Type a keyword into the search bar or click the Browse category option to filter the results.