Verokortti, tax deduction card is being delivered to you around these times.
Tax deduction card is valid from February 1st onwards, so you need to give it to your employer by then (or depending on which day they'll pay your February salary). But the bottom line is that you need to give the card to your employer, otherwise they will snip 60% off from your salary. You need to select whether you want the deduction to be calculated based on your monthly/biweekly/weekly/daily salary (option A), or based on your estimated total income from Feb to Dec 2012 (option B). Incase you end up paying too little amount of taxes, they'll send you a bill later on. And if you don't end up earning as much as expected and deducted, they'll pay you back next year.
After giving the card to employer, all you need to do is lay back and enjoy of what you'll get in return for your tax money: rather good health care, world class education, maintained roads, Länsimetro and Opera, to mention few.