Overview
QR codes cannot be generated in the system. They can be added to invoices by uploading them as an image under the Advertising on Invoice setting
Steps
Create a QR code using a free QR code generator that links to your Google Review page.
Download the QR code as a PNG image.
Go to Settings > Workshop Details > Invoice.
Under Advertising on Invoice, upload the QR code image.
Save the settings.
Result
The QR code appears at the bottom of printed invoices.