How Much Do You Need to Pay as a Sole Trader?

If i have to pay nine dollars brokerage when i buy shares or sell shares, can i claim the brokerage on tax? Not as a straight tax deduction, but it goes into the calculation of your cost base. There's a question here, im what if the shares, throughout the year don't pay dividends? They'll have to tell the aty o anything like that. But no need to declare anything if nothing was paid.