Does he have any investments listed on his financials? May not be specifically identified just as a Mutual fund investment. If not, I agree, something isn't right. However, if he's claimed a foreign tax credit (I think this means he's paid tax elsewhere) he's already admitting to CRA that he's got income from it so chech the income lines.
If you think he's cheating on his taxes (daycare expenses), you can report him even anonymously. If someone is reported, they'll eventually get to an investigation on that person and if he's got no receipts to back-up a daycare claim they'll be disallowed and he'll have to repay the tax on it and possibly penalties.