I used to work with guy that hadn’t filed a return in 20 years. Died in a car accident and the IRS never caught on. If I am late even a day with quarterly payments I get a notice. Go figure.
I heard about this one case where a “tax protester” died. His daughter was prepping the estate for probate and felt the need to balance the books, so she set about filing over 10 years of back taxes that had never been filed.
When she finished she discovered that the old dumbass had substantial refunds due for every year he was “protesting” by not filing! And since he was dead they were unrecoverable.