Let’s just take 95% as a true figure … first of all the 5% you don’t get back is a straight up loss. The rewards you get at the end of the month are fine (eg cash back) but you’ve missed out on earning interest on the money you “get back”

Card network fees (the part credit card users don't get back) are about the same for the European payment systems. For card users on net there is essentially no difference.

The interest argument of course is nonsense because the opportunity cost ia outweighed ~50x by the interest benefit you receive from the entire purchase going on credit vs just the 2% interchange.

“Of course”.

Thanks for responding — can you clarify this interest benefit you are talking about?

You are able to buy now, but not pay until 30 days later, paying no interest unless paid in full. Which means YOU earn interest on your money during that period...

Oh duh! Pardon my ignorance; that makes perfect sense, I guess my mind was elsewhere

If you don't know anything about it, why would you call it a tax?