Norway has been on a pre-populated system for all tax returns for a few years now, and last year transitioned to "silent consent", i.e. if you don't register any changes before the deadline, it means you accept the prepopulated values. From the statistics I've seen, ~60% don't register any changes, while ~20% register additional information, ~10% correct errors and ~10% register both additional information and correct errors. A lot of the additional info and corrections is stuff like kindergarten expenses (which are tax exempt up to a limit of $3000/year) or donations to charities, since it's up to the kindergarten or charity to register these, and they often forget or get things wrong.