QR codes for charitable donations

Good morning

I was wondering if anybody used QR codes for charitable fund donations and how they made this work and ensured that fake QR codes were not being used?

We have explored the use of QR codes to help promote our charitable funds and increase the level of day to day donations which are received but we have found that solutions are fairly expensive to set up and maintain.

Do any other charitable funds make use of QR codes for donations and what processes do you have in place to ensure fake QR codes are not placed over the genuine ones so fraudsters benefit from the money given?

Any suggestions gratefully received