One thing that I am sure of is that if you borrow money or use margin to buy Canadian stocks, the interest is deductible from your capital gains.(or if you have losses, the interest acts like a loss, and in the future if you have capital gains, you have the deduction)
When I first used an accountant 4 years ago, I told him I used margin and borrowed money from my line of credit in the past.
I still had my receipts.
He worked it out, said I overpaid, and I got a cheque in the mail 2 months later for $6000. I was really happy.

I recommend using a good accountant.
You can do all the preliminary bookwork yourself, for each stock you buy and sell.
Most brokers give a year end summary.

Before my time, you used to be able to deduct your losses from your regular income.
That was sweet.