"File a tax return"! I can never work out whether the Canadian and US governments are too lazy, too naive or too incompetent to do tax properly!

I've never filed a tax return in my life. Every job I ever had, HMRC were informed of my salary, worked out my tax code, and collected the correct account of Income Tax and National Insurance from my employer every month before I received my net salary. Any tax I overpaid would be promptly and automatically refunded at the start of the next tax year. Only the self-employed fill out tax returns, and they are gone over by a bunch of eagle-eyed sadists convinced that they're lying through their teeth!