My employer pay taxes for me based on either a table or percentage (this is up to me). At the end of the year our tax authorities sums everything together (income, capital gains, ownership, debt and so on) and sends me my preliminary tax report for me to verify and make changes to. For normal people it's usually correct with most deductibles already accounted for. It's easy to fill in any other deductibles or income that is not already accounted for. This year it ended up with the government owing me approx. $2000.