Most tax penalties are not the result of owing money. They are the result of a date passing quietly while you were busy. Here is the shape of the year.

The dates most individuals care about

  • Mid-January — fourth-quarter estimated payment for the prior tax year is due.
  • Late January — employers and payers must issue W-2s and most 1099s. If one has not arrived by early February, that is worth a phone call.
  • April 15 — individual returns are due, along with any balance owed and the first estimated payment of the new year. Prior-year IRA contributions also close on this date.
  • October 15 — extended individual returns are due.

An extension extends the filing, not the paying

This is the single most common misunderstanding we see. An extension gives you six more months to file the return. It does not give you more time to pay. If you expect to owe, estimate it and pay by the April deadline — otherwise interest and a failure-to-pay penalty start accruing even though your extension is perfectly valid.

Business deadlines

  • March 15 — partnership (Form 1065) and S corporation (Form 1120-S) returns, and the K-1s that go to owners. Extended to September 15.
  • April 15 — C corporation returns (Form 1120) for calendar-year filers. Extended to October 15.
  • January 31 — W-2s and 1099-NECs must be furnished to recipients and filed.

If your business is not on a calendar year, these shift — the deadline generally falls on the fifteenth day of the third or fourth month after your fiscal year ends, depending on entity type.

Quarterly estimated payments

If you are self-employed, have significant investment income, or otherwise receive income without withholding, you are likely making four payments a year. The periods are not even quarters, which catches people out:

  1. April 15 — covers January through March
  2. June 15 — covers April and May only
  3. September 15 — covers June through August
  4. January 15 of the following year — covers September through December

When a deadline lands on a weekend or holiday

It moves to the next business day. This is why April 15 sometimes becomes April 17 or 18 — and why it is worth confirming the current year's date rather than assuming.

What happens if you miss one

Two separate penalties exist, and they behave differently. The failure-to-file penalty is substantially larger than the failure-to-pay penalty. That leads to a rule worth remembering: if you cannot pay, file anyway. Filing on time and arranging a payment plan costs far less than staying silent.

Give yourself a buffer

Our appointment calendar fills from February onward, and the last two weeks before April 15 are the busiest of the year. Booking in January or February means we have room to ask questions, look at planning opportunities, and take our time. Booking on April 10 means we are working against a clock.