Not everyone can scan.
Some customers can't or won't use a camera. The card should still work for them.
A typed alternative
Every card includes a short web address customers can type, leading to the same page.
Readable text
Text on the card is at least 9 points with strong contrast, and the call to action says what happens: "Scan to pay Corner Deli" rather than "Scan me".
The page after the scan
The payment page meets WCAG 2.2 AA, works at large text sizes, and doesn't time out while someone is reading.