As I said, this would be one of the most pathetic and inept scams going if it was a scam as it is very easily picked up
The typical scam for businesses like this is either under declaration of revenue (cash jobs) or over declaration of costs (fictitious invoices). With fictitious invoices the way it works is that the company actually pays the invoices (otherwise they would sit on the books forever and look suspicious) but the recipient of the cash is some bank account connected to the owner of the company
I remember a Chinese Restaurant that was investigated and it was the number of foil dishes that were being used that were their downfall.
The number being used far exceeded the number of meals they claimed they were selling, and this led to the proof of undeclared sales