Most filers receive all their income from sources required to file how much they paid to the filers. The forms are all matched electronically. “Ah, you missed 15 dollars in interest” does not require some gun carrying swat team to descend on the filer. They need 87000 more agents like a moose needs a hat rack.
When I accidentally underpaid my Maryland state tax on my last Maryland tax return I had to do (I moved to Florida), they eventually found me and told me the remaining amount I owed plus a small penalty. They certainly didn’t need an armed goon to tell me that; just a note in my mail.