Do you mean that he only declares a third of his income for tax purposes, and that the income he will state on any financial disclosure is actually a lie? I assume he gets paid cash for a lot of the work he does? Have you suggested to him that for anyone to make an informed decision about SM he at least needs to be honest about his income? My ex husband and I are both self-employed and it made things very difficult with agreeing a split as he became extremely creative with his accounting! I do wory that one day I will no longer be able to stop myself making the phone call to HMRC.