It's in all walks of life Melisandre.
I did a spell in the drinks industry catching out wayward pub and club licensees. It wasn't hard, most were incredibly lax and sloppy in their methods. But I did find the odd one or two sophisticated methods used. As in most things in life, 'follow the money' is good advice and greed is often the Achilles heel. But when it's all cash you can draw inferences, but the proof can remain stubbornly elusive.
To my eternal embarrassment, I was in a pub fixing a one-armed bandit late one night. I did what was necessary, carried out a test, closed it down and said my goodnights to the landlady. Next morning, the first call on my rota was that pub again. As I entered, the landlady gave me a beaming smile and handed me a bag of cash, explaining that was my share of the booty. I'd only left the previous night leaving the damned machine set on jackpot payout, hadn't I!
Rather a difficult conversation with the boss ensued.
I had stumbled onto an easy and virtually untraceable fraud, especially if operated in clubs where the jackpots were so much higher and security far laxer. - And in later years, I saw quite a few variations of this.
Of course it'll fit; you just need a bigger hammer.