When the author says "add QR codes on bills so that consumers can easily extract their consumption data and make better choices", I think they mean "bill" as in a printed or written statement of the money owed for goods or services, rather than "bill" as in US banknote.

To be honest, it's still a bit of a WTF in this particular article given that there's plenty of behavioural evidence that (i) people really don't like scanning receipts into tracking systems, even when they're being paid to do so by getting their expenses refunded (ii) most consumers don't know or care what a QR code is

Yes, bill means receipt in British English.

It doesn't so much mean receipt as "invoice" (e.g. for taxes or utilities) or "check" (e.g. in a restaurant)

In most restaurants you would ask for the bill, then when you pay, you will receive a separate receipt.

The receipt is proof of payment.

Yes, that's better put.

"bills" = "invoices" in British English

(Edited for rightness)

Other way around surely?

Yes, sorry. I've corrected it.