How Quarterly Estimated Tax Actually Works
The quarters are not quarters
The four payments cover unequal stretches of the year. The April payment covers January to March, but the June one covers only April and May, and the September one covers three months from June to August. The last payment, due the following January, covers September to December. Dividing your expected bill into four equal pieces and paying them on those dates works fine; assuming each date covers three months does not.
Weekends, holidays and why a date moves
When the 15th falls on a Saturday, a Sunday or a holiday, the deadline moves to the next business day — and it can move more than once. In January 2028 the 15th is a Saturday and the Monday after is Martin Luther King Jr. Day, so the payment is not due until Tuesday the 18th. Washington D.C.'s Emancipation Day moves federal deadlines too, because the IRS is headquartered there, which is why some April deadlines land on the 17th or 18th.
Frequently Asked Questions
Do I have to pay quarterly at all?
Federally, only if you expect to owe $1,000 or more for the year after withholding and credits. Below that no payments are required. If you also have a W-2 job, increasing the withholding there is an alternative to estimated payments and has the advantage of being treated as paid evenly across the year.
What happens if I miss one?
You owe an underpayment penalty, which is interest on the shortfall for the period it was outstanding rather than a flat fine. Paying late is better than not paying — the charge stops accruing when the money arrives.
Are state deadlines the same?
Often, but not always, and the amounts can differ even when the dates match. California is the notable exception: it wants 30% by 15 April, 40% by 15 June, nothing in September and 30% by 15 January.