Just a guess, but he is probably paying his employees in cash so they don't have to pay taxes. However, unless you have a substantial basis to believe he is involved in illegal activity, no SAR is required. However, you will get some argument here that tax evasion or "conspiring" with someone else to avoid payment of income taxes is reportable. Unfortunately, it is a judgment call. Some are adamantly opposed, while others feel it is the right thing to do. Personally, I think it is the right thing to do since I have to cover for the taxes these people do not pay.