The latest statistics I could find for Denmark (2009) say 80% accepted the tax as prepared by the government, around 18% edited it online and 2% sent in paper.

The latest statistics I could find for Denmark (2009) say 80% accepted the tax as prepared by the government, around 18% edited it online and 2% sent in paper. Recently most things are automatically filed and unchangeable, even down to something like charitable giving -- if you send Amnesty some money every year, they are responsible for telling TAX so you can get a deduction. If there's an error, you have to contact your charity, not TAX. If you paid too much money in tax, there's one specific account every citizen has, that's used by government to send you money. No checks.