The Counterfeit Credits intel quest is one of the trickier ones you can undertake on Star Wars Outlaws' starting planet of Toshara. You'll encounter this quest once you reach good reputation with the Pyke Syndicate and speak to the Pyke in their district who's sitting at a table near the card room.
He explains that someone is circulating fake credits in a bid to undermine the gang and he wants you to find out who it is. The intel gives you a search area in the market, but it isn't at all clear how you're supposed to determine which trader is doling out the fake cash. Here I'll explain where to find the market trader in question and complete the quest.
The trader you're looking for is Hen Puon in the Mirogana Market just to the north of the Pyke Syndicate district in Mirogana. In order to uncover the counterfeit credits, you need to sell a valuable item to Hen Puon. Upon receiving the credits, Kay will call him out, and Hen will claim innocence, directing you to the soup kitchen and the person who gave them to him, i.e Crimson Dawn.
The soup kitchen intel directs you to the Crimson Dawn district to the north of the market. It'll be easier to access this if you have a good reputation with them, but if not, you can always sneak into the district through the vent to the right of the soup kitchen entrance—just get Nix to hit the switch and open the vent.
The credit stash you're looking for is in the same room as the Crimson Dawn vault, which is in the restricted area. I recommend hopping up onto the landing pad via the platforms to its right, then using Nix to hit the switch and stop the fans so you can crawl through. Then all you need to do is climb down the ladder into the room and investigate the box at the back.
You'll be given a choice to warn Crimson Dawn or tell the Pykes, which will mean more rep with either. Once you leave the district, you'll have to report back to Eleera or the Pykes depending on your choice, concluding the quest and giving you that rep.