Well to be fair, there's only a single line, in a single movie (First Contact) where a character comes right out and states "money doesn't exist."
off the top of my head
Don't tell me they don't use money in the 23rd Century?
Well, we don't.
Pretty sure they attempt to definitively suggest that money is obsolete in the 23rd century onwards on many an occasion.....though they later tried to pretend that what they meant was that money (actual notes and coins doesn't exist)....but yeah currency does (credits) but not ya know, money as you know it - that's not consistent with the initial premise but i guess it's consistent with the premise that money (notes and coins) no longer exist (though they are conveniently vague about the distinction)