Many, many years back, working for a small craft Trades Union, I totally accidently discovered a fraud, whilst the person who was committing it was on holiday. Had been doing this for a couple of years, and accounts had actually successfully gone through two audits. I was by sheer accident that I discovered it, and passed on the information straight away. Upshot was, police were involved, and the atmosphere in that office for the next few months was horrific. She was arrested on return from holiday, and all sorts of extra procedures put in place to prevent any repetition. Must say over that first few weeks I often wished I had not noticed the forgery which led me to questioning things - but it was our members money she was ripping off, so was glad that it had all come out. Just wondered how gullible we had all been for so long.