be on the fiddle

To engage in deceitful, fraudulent, or dishonest means of obtaining money. My career will be over if anyone ever finds out I was on the fiddle during my time as the company treasurer. Politicians will always be on the fiddle in any government, looking for ways to use their positions of power to earn a bit more money. A: "I can't believe that Margaret was actually on the fiddle this whole time." B: "I know! She's the last person I would have suspected of stealing money."