Review QR Code Generator

On the invoice and on the job-done card, in that order. Van signage looks good but almost nobody scans a code on a moving vehicle. The moment that works is when the technician hands something over and says what it is for.

About an inch square is the practical floor for a phone camera at arm's length. Smaller than that and it needs good light and a steady hand, which is not what you get on a doorstep.

Yes. The URL is encoded into the pattern itself, so a printed code points at that address permanently. If you expect the destination to change, point the code at a short link you control and change where that redirects.