Yes, it is unethical and illegal. Some poor retail drone could get stuck with the bill or even lose their job. Now, if that $20 was the only thing between my family and starvation, then I’d consider it.
Of course it’s unethical and illegal. 
But I wouldn’t call COSTCO a poor retail drone.
Would you feel better if I passed it at a Gas Station? Come to think of it…
The last time I tried to pass a $23 bill, they immediately knew it was counterfeit. :smack:
One thing that I wonder about: When I delivered pizza, I collected cash and checks throughout my shift and then settled up with the restaurant at the end of my shift. My orders would be added up and I’d pay for them and whatever was left over was my tips.
The most organized thing I ever did was keep a running tally in a notebook of how much I’d collected and how much the totals were so I’d have an idea of how much my tips were before I checked out. At the end of a busy night, I’d easily have $500 cash or more and no way of knowing where any individual bill came from.
Those markers don’t work, they’re a scam.
They contain dilute iodine which reacts with starch used as a sizing on copier paper, but if the paper the counterfeit is made of doesn’t use starch-based sizing then it won’t react (turn black). Anyone who relies on one of those pens to detect moody cash is being foolish. You could really screw with people if you rub a cut potato on all your cash.
Some SDMB poster said that if a merchant uses that marker on a bill he/she presents, then he will ask to borrow that marker and use it on the bills he receives as change. Throws 'em for a loop. I thought that was funny.
Passing fake currency to buy something is essentially stealing. Whether or not one thinks insert store name here is ethical themselves or whether they have enough money to back it up is irrelevant, since the losses always gets passed down to the consumer (which in turn, affects everyone).
Costco can afford it, but perhaps the poor clerk taking your bill can’t afford it. Some retailers will insist the clerk make the shortage up out of his pocket, or write him up.
Total opposite of the way I did it when I delivered - I’d come back and cash out after each run. As a matter of fact, we had to, because when the manager checked us in after each run, that’s when the system would determine how long the deliveries had taken.
-Joe
Why in god’s name is Domino’s calling you about a Pizza Hut pizza? This story just gets more and more confusing.