[ProblemFactory]

It's difficult to predict what the outcome of the situation will be.

It could be that the founder keeps himself officially "unaware" on purpose. This way he can shift the blame to others if it becomes public, and still make a profit from defrauding clients.

If he is truly unaware, you will still be up against two senior employees who will deny the accusations - and you may end up looking like the "crazy disruptive new guy".

I would suggest gathering as much documentation as you can on the excessive billing. Then approaching him without directly accusing the senior employees, and pitching it as a way to improve the business. "I have figured out why the clients left, we made mistakes on their bills!" instead of "Your senior people are defrauding clients".

If the founder seems to be unconcerned about the "mistakes", start looking for a new job.

[throwawayagency]

Interesting way of posing the situation to the founder. Thanks for this.