Where I live (Norway), it goes like this - at the most basic level:
(1) Annually, the gov. issues me a tax "card", which basically just contains some tax-information about me - like what rate I should be paying. This is based on my previous year of income, or I set one myself, based on what income I believe I will have this year.
(2) My employer requests that card/information from the gov., and will deduct the taxes I owe on my salary. My employer then pays in those taxes, to our tax agency.
(3) Once a year, I will receive a document that shows my income, how much I've paid, and what my balance is. If it looks good, I don't need to do anything. If I want to add certain deductions, external/unreported salaries, or what not, I'll have to fill them inn on that document.
That's it. If my balance ends up negative, I have to pay back taxes. If it's close to zero, I nor get or pay anything back. If it's positive, I get back the difference.
Sure - it can become complicated if you have a ton of investments, companies, deductions, and what not - but for regular people? It's a breeze. For most, actually, the only active thing you have to do, is to check that your tax rate looks OK, and that takes you under 5 minutes. Once a year.