I read this story in an anthology of science fiction short stories. I was in grade 6 and it was 1969.
It was about a man that goes to buy something with money but the store was cashless. Finally they sold him the item but had to put what was to be his change on credit.
I can't seem to find it anywhere but it made a huge impression on me and I thought to myself back then that I could see it happening. Lo and behold it is becoming reality. I thought the name of it was "Yemon."