> Normally, when you have expenses, you deduct them off your revenue to find your taxable profit. If you have $1 million in sales, and $900k in costs, you have $100k in profit [..]

I'm not sure it's helpful to simplify quite that much, doesn't this usually depend on whether we're talking about operating expenses (typically rent, utilities, salaries, supplies) or capital expenditures (typically buildings, land, intangibles...)?