dennis@home wrote:

charles wrote:

How does your industry tell the difference between a bill printed by the
supply company on their laser printer and on printed on the customers'
laser printer.

With most printers it is possible to identify which printer it was
printed on including personal ones. I doubt if they perform the
necessary checks or even know you can do it

Even if they do, how are they expected to know that CheapBlueSparks Ltd
uses a printer with a specific serial number?