Quarterly estimated taxes: a simple calendar for owners
When to pay, how much to set aside, and how to avoid underpayment penalties.
Most tax authorities expect businesses and their owners to pay tax as income is earned, not in one lump sum the following year. For a business with steady profit, that usually means an estimated payment four times a year rather than one annual bill. Missing a payment, or underpaying by too much, typically triggers an interest charge on top of the tax itself — not a one-off penalty, but a running cost for every day the payment was short.
Work out what to set aside, not what to pay
The easier version of this problem isn't predicting your exact quarterly bill — it's setting aside a fixed percentage of profit as it comes in, so the quarterly payment is never a surprise. Most owners land somewhere between a quarter and a third of profit, depending on their structure and local rates. The number matters less than the habit: move it to a separate account on the same day you review your monthly numbers, before it has a chance to look like spare cash.
If last year was unusually strong or unusually weak, don't anchor this year's set-aside to last year's number. Base it on this year's actual run rate, reviewed monthly.
Build the calendar around your close, not the other way round
Estimated payments are easiest when they sit on the same calendar as your monthly close. If your books are closed and reconciled by a fixed date each month, you already know your year-to-date profit by the time a quarterly payment is due — there's no scramble to reconstruct three months of transactions right before a deadline.
- Set aside the percentage on the same day every month, not just near a deadline
- Review year-to-date profit against your estimate at each close
- Confirm the exact due dates for your jurisdiction and put them on a shared calendar, not a sticky note
- Adjust the running set-aside if a quarter is materially ahead of or behind plan
What actually causes an underpayment penalty
In most systems, the penalty isn't really about getting the number exactly right — it's about paying roughly in line with either your current year's income or your prior year's bill, whichever your local rules use as the safe harbour. A good bookkeeping-driven estimate, reviewed each month, keeps you inside that range without needing to predict the future with any precision.
If this already sounds like more process than you have time for, that's the part we take off your plate — the monthly close, the running estimate, and the reminder before each payment is due.
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