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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.
To proceed, you can visit QuickBooks App Center to check for an application that can help you add a QR code to your invoice. Another way is to go to your QBO account's Apps menu.
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.