[sokoloff]

It’s not late filings as much as late payments (late quarterly estimated taxes, under-withholding beyond safe harbor rules, etc.)

Lots of people who are self-employed or who make a high W-2 income and receive irregular payments/gains (bonuses, RSU vests, capital gains) fall into this category.

Late filings are almost trivial to avoid; late payments are significantly harder to entirely avoid as, depending on your tax situation, many of the payments are due 12, 9, 6, or 3 months earlier than April 15.

[SoftTalker]

I suppose. I've had years in the past where I had sporadic self-employment income, and I filed estimated payments only for the quarters where I had income, maybe even was late or combined a couple of quarters every now and then. I never got penalized as long as the amount I owed for the year had been paid by April 15. Maybe I was a small enough fish that they just didn't care.

[sokoloff]

Most likely you met one of the safe harbor tests.

The dunning for getting this wrong is automated, so if you didn’t do it right and didn’t pass a safe harbor, they’d have sent you a notice.