My Ex is excluding taxable benefits from his income

I have been divorced for 5 years now, and have a separation agreement in place which requires the payor (my ex) to provide me with his income tax return and Notice of Assessment annually.

I have just discovered that he has not been including his taxable benefits, namely his company vehicle for personal use.

I have approached him about that and he referred me to his payroll rep. She advised that she is not including on his T4.

Not only this, I know that he is intentionally keeping his income at the original amount from 2008 to avoid paying anymore in support.

He has a much better position with the company, yet there is no increase in his annual salary. I believe he is being paid in other ways.

Is it worth it to push this issue using a lawyer? He has always got me to back down because he can afford a lawyer and at the time, I could not.