I recently started working in an arrangement neither me nor the person who hired me has done before. Someone who works as a contractor for a company got a budget to hire me as a (sub)contractor. He has an unincorporated company. He has agreed to provide me with a T4A and withhold tax for me. He is now asking me what tax he should withhold, like CPP or EI? What benefit is it to me to have my client withhold tax instead of doing it myself? Other than CPP or EI what else is there?