The IRS does not wait until April to see if you paid enough. It checks four times a year, and it can charge a penalty for any quarter where you came up short.
Paying your full tax bill by December 31 does not undo that. The shortfall from June already happened, and the penalty for it does not disappear just because you caught up later.
What this means for you
- Missing one estimated tax deadline creates a penalty for that quarter, even if you pay in full by December.
- Freelance, rental, side business, investment, and consulting income with no withholding usually means you owe estimated payments each quarter.
- There is a safe harbor that protects you even in a big year, and it is based on last year’s return, a number you already have.
- Set calendar reminders for January 15, April 15, June 15, and September 15 right now.
What are estimated taxes, actually?
Most employees never think about this because their employer sends tax money to the IRS out of every paycheck. That is withholding, and it happens automatically.
Estimated taxes exist for income where nobody is withholding anything on your behalf.
That includes freelance or contract income, rental income, side business profit, investment gains, and consulting fees. If any of that applies to you, the IRS expects you to send in your own payments, four times a year, roughly matching what you earned in that period.
What people get wrong
- They think a year end catch-up payment fixes everything. It does not. The underpayment penalty is charged per quarter, so a late payment in December does not erase a penalty from a quarter you missed in June.
- They assume any withholding at all means they are covered. A part-time job with a W-2 does not offset a large rental profit or a big consulting invoice if nobody is withholding tax on that side income.
- They wait until they see the total tax bill at filing time. By then, three or four quarters have already passed, and each one is judged on its own.
The numbers
These are the four payments and the dates they fall due. The periods are not equal lengths, which catches people out. Missing any one of them can trigger a penalty tied to that specific period, not the year as a whole.
| Payment | Covers income earned | Due date |
|---|---|---|
| 1st payment | January to March | April 15 |
| 2nd payment | April and May | June 15 |
| 3rd payment | June to August | September 15 |
| 4th payment | September to December | January 15 of the following year |
Note the last one. The payment that closes out a tax year is not due until the middle of January in the next one, which is why January 15 shows up on a calendar of reminders alongside the other three.
The shortcut most people miss
You do not actually have to predict this year correctly. There is a safe harbor, and if you land inside it you are generally protected from the underpayment penalty even if the year turns out much bigger than you expected.
You are inside it if your payments across those four dates add up to the smaller of these two amounts:
- 90 percent of this year’s total tax. Accurate, but it requires forecasting a year that has not finished yet.
- 100 percent of last year’s total tax, or 110 percent if your adjusted gross income last year was above $150,000, or above $75,000 if you file married filing separately.
The second one is the useful one, because it is a number that already exists. One clarification that trips people up: it means the total tax line on last year’s return, not the check you wrote in April. Those are two different figures, and the one you want is usually much larger.
Take that total, apply 100 or 110 percent depending on which side of the income threshold you were on, divide by four, and pay that on each date. A consultant who lands an unusually large project in August is then not punished for failing to see it coming.
The steps
- Set a calendar reminder today for January 15, April 15, June 15, and September 15. These repeat every year.
- List every income source with no withholding: freelance work, rental income, side business profit, investment gains, consulting fees.
- Pull last year’s return and find the total tax line. That is your safe harbor number. Divide it by four.
- Pay that amount on each of the four dates, and keep a record of the date and amount in case a period is ever questioned.
- If your income changes a lot during the year, call your preparer mid-year rather than waiting until filing season to adjust.
Who this does not apply to
If you are a W-2 employee with no significant outside income, your employer’s withholding is probably already covering you. This is not aimed at you.
It also does not apply if your only extra income is small and already covered by adjusting your W-4 withholding instead of making separate payments. Some people prefer to handle it that way, and that is a legitimate option to discuss with whoever preps your return.
Philip’s take
Of the two ways to cover extra income, quarterly estimated payments or adjusted W-4 withholding, I usually rank estimated payments first for anyone with irregular income like freelance work or rental profit, because the amount owed changes period to period and a fixed withholding adjustment cannot flex with it.
And I would rather see someone use the prior year safe harbor than try to forecast. Forecasting is where the penalties come from. Last year’s number is already sitting on a return you filed.
A calendar reminder costs nothing. A missed period costs you a penalty you cannot undo later, no matter how much you pay by December.
This week, open your phone calendar and set those four reminders: January 15, April 15, June 15, September 15.
If you are not sure whether your income needs estimated payments or a withholding adjustment, our office is glad to help you figure out which one fits.
This article is general information, not tax advice for your particular situation. Rules change and individual facts matter. Talk to a CPA before acting on anything here.