I work in POS systems, and thus know various kinds of receipt printers rather intimately. It is surprising how much variation the command sets have when it come

I work in POS systems, and thus know various kinds of receipt printers rather intimately. It is surprising how much variation the command sets have when it comes to printing barcodes, and especially for more complex ones like QR codes. Older ones don't even support them, you have to resort to software-rendering and printing images instead. And the image-printing commands are just as messy. It would probably be easier to add some kind of OCR functionality into the app to automatically read and parse some kind of textual order ID from a receipt than to ensure that QR code printing works fine on 30 different POS printers from 20 different manufacturers, of which some are over 10 years old. Though a combination would probably be best: print QR codes whenever possible, prefer them when scanning, but when no code is found, try to OCR the receipt and find a textual ID.