Was there anything in the original Star Trek to suggest that humans no longer had money?

I went to a grocery store tonight and paid for some vegetables with a five-dollar bill (legal U.S. currency). The guy said he didn't have anything to give me change with. The use of actual money is already discouraged, frowned upon, almost shamed. It's not a stretch to imagine that by the 23rd century (or whenever Star Trek is supposed to be) humans will no longer have money.

The show mentioned Federation credits as a currency several times, there was money.

Although I dont know if there was cash.

I think it was always intended as part of the progressive utopian future... Where world hunger, war, poverty, racism, and all other ills of the 20th century had been done away with.

My knowledge of The Original Series is not encyclopedic enough to say when or how this was ever explained in the show.

As the movies (starting with 2) became even more focused on military action adventure stories, TNG doubled down on the utopian future, giving the Captain a right hand empathetic counselor, and degrees in diplomacy and debate in place of Kirk's "kiss or punch" "diplomacy".

I do think the "no money" thing paints the writers into a corner fairly frequently. Drama is driven by conflict, and removing money removes a lot of potential for conflict.

Didn't stop McCoy from hiring a private ship to Genesis in Search for Spock though...

Kirk only implied that physical money was no longer used, not that actual currency and trade had ceased (which later shows mistakenly pursued (too aggressively) as an idea).

Given that we're close go that already, it makes sense.

Star Trek 4 The Voyage Home. Kirk says "These people are still using money". Then goes off to sell his antique specs. But w.r.t. the original question, I always took it for granted.