Tax seasons: the four dates and the surprises
Tax season surprises are almost never surprises — they're withholding that stopped matching the income. This letter covers the four dates that structure the American tax year, the income types whose withholding quietly under-collects, and the two habits that make April boring.
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The four windows (the whole calendar)
| Window covers | Payment due | Who cares |
|---|---|---|
| Jan 1 – Mar 31 | April 15 | Everyone — plus the annual return for individuals |
| Apr 1 – May 31 | June 16 | Estimators, plus anyone whose bonus landed in Q2 |
| Jun 1 – Aug 31 | September 15 | The quarter with no natural reminder |
| Sep 1 – Dec 31 | January 15 (next year) | The catch-up that funds the holidays' quiet cousin |
Cover at least 100% of last year's total tax (110% above the income threshold) through withholding and estimates, and underpayment penalties generally disappear — even if this year's income jumps. The rule turns 'how much will I owe?' into 'what did I owe last year?' — a number you actually know.
The income that under-withholds
- RSUs at vesting: often withheld at a flat rate below your marginal bracket — the gap is yours to cover.
- Bonuses and commissions: the 'supplemental rate' is a withholding number, not your real rate — the reconciliation happens in April.
- Equity sales, dividends, interest, side income: usually no withholding at all — estimates or extra W-2 withholding cover them.
- RSU + bonus in the same year: the classic double-surprise — both under-collect, and they arrive in the same April.
The fix is mechanical: when a big non-regular payment lands, either send a same-week estimate or file a new W-4 with a extra fixed dollar amount for the remaining paychecks. Either way, the calendar — not April — absorbs the correction.
The two habits that make April boring
- One folder, one tax year: every tax-relevant document (W-2s, 1099s, K-1s, withholding confirmations, the RSU statements) lands in the same place — digital is fine, retrievable is mandatory.
- A 30-minute January reconciliation: pull last year's total tax, check the safe harbor, and write down the four dates with the amounts. That half hour is the entire difference between a tax season and a tax surprise.
The professionals who never dread April aren't the ones with simple returns — they're the ones whose withholding was corrected in June, not discovered in April.
The Quiet Money Review, letter four
Frequently asked questions
What if I already got surprised this year?
Pay promptly — the penalty accrues by the day, so waiting makes it worse, not better. Then the January reconciliation (this letter's habit) is how it never happens twice — the safe harbor is forgiving to those who learn once.
Estimated payments or extra withholding — which is better?
Withholding is treated as paid evenly across the year regardless of WHEN it lands — a genuine advantage over estimates for fixing an early-year gap. Estimates win on flexibility for irregular income. Many professionals use both: withholding as the base, estimates for the lump events.
My return is genuinely complex — is this letter still for me?
The letter is the calendar layer that sits UNDER the complexity: the four dates and the safe harbor apply no matter who prepares the return. The complexity belongs with your professional; the calendar belongs to you.