I had to ask about 5 people "wait, so I REALLY don't have to file taxes?? Seriously?" after I moved to Ireland before it really sank in. The answer is no, and if you need to change your tax situation (for instance, if you get married) a simple email to your local PAYE office will often suffice. I email DubNorthCityPAYE@revenue.ie and usually get a response within a few days.

Of course, the sad thing is that I actually DO still have to file taxes. To the US.