I live in Germany, which is said to have one of the most complicated tax systems known to man. If I had one (realistic) wish for a German government, it would be to do it like Finland.
Sadly there is a whole branch of people working on this, without any interest to make it easier..
Norway is very simple too. Most people can just do nothing at all. The way it works is that the tax authority creates a proposed tax record and notifies you by SMS or email or both or even by letter if you ask for it. If you agree that it is correct you don't need to do anything at all, otherwise you log in to the web site and adjust whatever needs adjusting in a bunch of simple forms.
The tax authorities also have a duty to calculate the taxes in the way that benefits you most.
In Portugal, of all places, it’s just a web form. This year it took me a grand total of 3 minutes to review all info and less than 10 clicks after logging in.
Just a few weeks ago, I logged into Elster, opened the pre-filled tax return (Belegabruf) and sent it. Instead, I could have filled the short and simple Vereinfachte Steuererklärung by hand which covers all common cases.
Most workers don't need to do anything to get their overpaid tax back thanks to the Lohnsteuerjahresausgleich.
Aldi (or Lidl) every year sell a Tax Prep software for 5 euros. Our in-laws buy a copy, install it, then pass it on to us (same key works on multiple PCs). The software's UI could use some...clarity in certain places but it is incredibly full-featured.
We've been happily using it to file our German taxes for years.
Sadly there is a whole branch of people working on this, without any interest to make it easier..