Most penalties we see are not the result of a dispute over the numbers. They are the result of a date that passed while someone was waiting to feel ready. Here is the shape of the filing year, and what each date actually requires.
The usual dates
These are the dates in a typical year. When one falls on a weekend or a legal holiday, it moves to the next business day, and disaster declarations can push dates back for affected areas — so confirm the current year’s calendar rather than relying on memory.
January 15
The final quarterly estimated payment for the previous tax year is due. Miss it and the underpayment penalty is calculated as interest on what was late, not as a flat fine.
January 31
The date by which employers must furnish W-2s and most payers must furnish 1099s. If a form has not reached you by early February, ask for it — you still have to report the income either way.
March 15
Partnership and S corporation returns are due, along with the K-1s the owners need to file their own returns. This is the date that quietly determines whether individual returns can be finished on time.
April 15
Individual returns are due, along with the first estimated payment for the current year, IRA and HSA contributions for the previous year, and C corporation returns for calendar-year filers.
June 15 and September 15
The second and third estimated payments for the current year. September 15 is also the extended deadline for partnership and S corporation returns.
October 15
The extended deadline for individual returns. This is a hard stop, not another extension point.
Two different penalties
It is worth knowing that failing to file and failing to pay are treated differently, and that the failure-to-file penalty is generally the more expensive of the two. That is the practical argument for filing on time even when you cannot pay in full: file, then arrange the payment separately.
If you cannot pay
The IRS has instalment agreements, and applying for one is routine. Interest continues to run, but the account stays in good standing and collection activity pauses while an agreement is in place. We can look at whether one fits your situation and handle the application.
State deadlines
Most states follow the federal individual deadline, but not all of them, and business filing dates vary more. If you file in more than one state, treat each one’s calendar as separate until you have confirmed otherwise.
A simpler way to hold all of this
You do not need to memorise a calendar. Two habits cover most of it:
- Book your appointment in January or February, not late March. Everything downstream gets easier.
- If you pay estimates, set four recurring reminders on the 10th of January, April, June and September — five days of buffer before each due date.
Clients we prepare returns for get deadline reminders from us as a matter of course, including the quarterly dates that apply to their situation.
This article is general information about how the tax rules work, not tax advice for your situation, and the rules change. Speak with a qualified preparer — we are happy to be that preparer — before acting on anything you read here.