Estimated Tax Calculator
Tax & IncomeQuarterly payments that keep you penalty-safe.
Income & tax already paid
More options
Enter your income to estimate your quarterly payments.
2026 Single tax brackets
| Rate | Taxable income over |
|---|---|
| 10% | $0 |
| 12% | $12,400 |
| 22% | $50,400 |
| 24% | $105,700 |
| 32% | $201,775 |
| 35% | $256,225 |
| 37% | $640,600 |
Your inputs
| Input | What it means | Your value |
|---|---|---|
| Tax year | The tax year your estimate uses. | 2026 |
| Filing status | Sets your brackets, deduction and thresholds. | Single |
| Net self-employment | Self-employment income after expenses. | $0 |
| W-2 wages | Employer pay already withheld from. | $0 |
| Other income | Interest, dividends and other income. | $0 |
| Federal tax withheld | Federal income tax already withheld. | $0 |
| Last year's total tax | Last year's total tax, for the safe harbor. | $0 |
Know what this estimate is based on
- Jurisdiction
- United States unless the calculator explicitly says otherwise
- Rules and time period
- Tax years supported by the selected calculator
- Scope and limitations
- Educational estimate only, not a tax return or filing determination. U.S. statutory-threshold tools use USD. Confirm current law and your facts with the relevant authority or a qualified tax professional.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Choose the tax year and filing status so the calculator loads the right wage base, tax brackets, and standard deduction.
- 02
Enter your self-employment income and business expenses, plus any wages, other income, and adjustments, so the tool projects this year's total tax (self-employment tax plus income tax).
- 03
Add the federal income tax already withheld and any estimated payments already made — withholding is credited evenly across all four quarters, while dated payments only protect the quarter they land in.
- 04
Provide last year's total tax and AGI so it can compare the 90%-current and 100%/110%-prior safe harbors and aim at the lower target.
- 05
Read the recommended quarterly installment, the four due dates, and the underpayment-risk readout — and check whether the $1,000 rule clears you or a balance still falls due at filing.
Formula
Estimated tax is what you prepay the IRS during the year on income that has no withholding — self-employment, freelancing, a side business, investments. This planner works in three moves. 1) Project this year's total federal tax Net self-employment income = self-employment income − business expenses Self-employment tax = 15.3% on 92.35% of net SE income (12.4% Social Security up to the year's wage base, 2.9% Medicare with no cap, plus 0.9% more on high earners) AGI = wages + net SE income + other income − adjustments − one-half of the self-employment tax Taxable income = AGI − your standard or itemized deduction Income tax = the progressive brackets on taxable income − tax credits Total tax = income tax + self-employment tax 2) Find the safe-harbor target Safe harbor = the LESSER of 90% of this year's total tax, or 100% of last year's tax (110% if last year's AGI was over $150,000, or $75,000 if married filing separately). Prepay at least this and you sidestep the underpayment penalty entirely, though any remaining balance is still due in April. If your total tax minus withholding is under $1,000, no estimated payments are required at all. 3) Turn it into quarterly payments Required estimated payments = safe-harbor target − tax already withheld Each quarter = (required − payments already made) ÷ quarters remaining Due dates: April 15, June 15, September 15, and January 15 of the next year. Withholding counts as paid evenly across the year; estimated payments are dated to each quarter. Only federal tax is modelled — the QBI deduction, Net Investment Income Tax, AMT, and state and local estimated taxes are left out.
Example
Say you're single and freelance full-time in 2026, expecting $100,000 of income against $20,000 of business expenses — $80,000 of net self-employment income, with no W-2 job and nothing withheld. Self-employment tax comes first: 92.35% of $80,000 is $73,880, and 15.3% of that is $11,303.64. Half of it, $5,651.82, is deductible above the line. Your AGI is $80,000 − $5,651.82 = $74,348.18; after the $16,100 standard deduction, $58,248.18 is taxable, which the 2026 single brackets tax at $7,526.60. Add the two together and your total estimated tax is $18,830.24. Because you had no large tax last year, the safe harbor is simply 90% of this year's tax: $16,947.22. With nothing withheld, that's the full amount to prepay — about $4,236.80 for each of the four quarterly due dates. Paying exactly the safe harbor keeps you penalty-free, though you'd still settle the remaining $1,883.02 when you file. Prefer no surprise in April? Prepay the whole $18,830.24 instead — about $4,707.56 a quarter.
Definitions
- Estimated tax
- Estimated tax is the income and self-employment tax you prepay during the year on earnings that have no withholding, such as freelance or 1099 pay, business profit, rent, or investment gains. You send it yourself in four installments using Form 1040-ES.
- Safe harbor
- Safe harbor is the prepayment amount that shields you from any underpayment penalty regardless of your final bill. You meet it by paying the lesser of 90% of this year's total tax or 100% of last year's, rising to 110% when last year's AGI topped $150,000 ($75,000 if married filing separately).
- Underpayment penalty
- An underpayment penalty is the charge the IRS adds when your timely payments fall short of the safe-harbor target. It works like interest, not a flat fee — applied through Form 2210 to each quarter's shortfall for the days it stays unpaid, so a missed early installment keeps accruing until covered.
- Form 1040-ES
- Form 1040-ES is the IRS worksheet and set of payment vouchers for figuring and mailing federal estimated tax. It walks you through projecting your annual income, tax, and credits, then splits the required total into four dated installments you remit through the year.
- Required annual payment
- The required annual payment is the smaller of the two safe-harbor figures: 90% of what you'll owe this year, or 100% of last year's tax (110% for higher earners). Subtracting expected withholding from it leaves the amount you must cover with quarterly estimates.
- De minimis ($1,000) rule
- The de minimis rule excuses you from estimated payments and penalty when your total tax minus withholding comes to less than $1,000. You still owe that balance at filing, but the IRS treats the gap as too small to require quarterly prepayment.
- Self-employment tax
- Self-employment tax is the 15.3% Social Security and Medicare levy on 92.35% of your net self-employment earnings: 12.4% up to the annual wage base ($184,500 in 2026) plus 2.9% uncapped Medicare, with an extra 0.9% over high-income thresholds. Half of it deducts against your income-tax base, and none applies below $400 of net earnings.
- Quarterly due date
- Quarterly due dates are the four deadlines for each estimated installment: April 15, June 15, September 15, and January 15 of the following year. The periods are uneven, and the final fourth payment lands in January, not December.
- Annualized income installment method
- The annualized income installment method lets people with uneven earnings size each payment to the income actually received by that quarter, instead of paying four equal amounts. It can lower or defer installments when money arrives late, but it requires Schedule AI tracking on Form 2210; this planner uses even quarters instead.
- Prior-year safe harbor
- The prior-year safe harbor lets you base payments on last year's total tax rather than forecasting this year's. Paying 100% of it (110% if last year's AGI exceeded $150,000, or $75,000 if married filing separately) blocks any penalty even when this year's income jumps — and a genuine $0 last year means no payments are required at all.
Good to know
Who has to send the IRS money four times a year
Estimated tax is the money you mail the IRS yourself, four times a year, on income that arrives with nothing taken out first. A salaried worker never thinks about this because an employer skims tax from every check and forwards it. The moment your income shows up whole — a freelance invoice, a 1099 contract, gig work, rent from a tenant, dividends, a capital gain — nobody is doing that for you, so the federal government asks you to settle up as the year unfolds rather than waiting for one reckoning in April. The practical trigger is simple. If you expect to owe at least $1,000 in federal tax after subtracting whatever is being withheld elsewhere, you are generally expected to make quarterly estimated payments. That sweeps in most self-employed people and freelancers, but also plenty of retirees, investors, and anyone whose side income outgrew the withholding on their day job. Owing the tax is not the problem; owing it without having prepaid it on schedule is what exposes you to a penalty. This calculator exists to turn that obligation into a single, defensible number per quarter. It projects your full federal tax for the year, finds the least you can pay in without tripping a penalty, credits anything already withheld, and divides the rest across the deadlines you still have left. Take the example carried through these notes: a single filer in 2026 with $100,000 of self-employment income and $20,000 of expenses. The tool reads out a recommended payment of $4,236.80 each quarter — not a guess, but the figure that keeps the IRS satisfied. Everything that follows explains where that number comes from, why it is usually smaller than your true bill, and how to avoid the traps that catch people who wing it.
Building this year's number: income tax on top of self-employment tax
Before the planner can tell you what to prepay, it has to estimate the whole bill, and for most users that bill has two layers stacked on each other. The first is self-employment tax. Your net self-employment income is revenue minus business expenses — $80,000 in the running example — and the SECA charge applies to 92.35% of it. On that base you owe 12.4% for Social Security, but only up to the year's wage ceiling ($184,500 for 2026, up from $176,100 the prior year), plus 2.9% for Medicare with no upper limit, plus an extra 0.9% once combined earnings pass $200,000 single, $250,000 married-jointly, or $125,000 if married filing separately. Below $400 of net earnings, none of it applies. For the example that produces $11,303.64. The second layer is income tax, and the two interact. Half of your self-employment tax — the regular part, not the 0.9% surtax — comes off the top as an above-the-line adjustment, lowering the income your brackets are figured on without reducing the SECA charge itself. So adjusted gross income is wages plus net self-employment income plus other income, minus your adjustments and minus that half-SE deduction: $80,000 − $5,651.82 = $74,348.18 here. Subtract your standard or itemized deduction, leaving $58,248.18 of taxable income, and run that through the seven progressive brackets, subtract any non-refundable credits, and floor the result at zero. That yields $7,526.60 of income tax. Add the two and you have the total the rest of the plan hangs on: $7,526.60 + $11,303.64 = $18,830.24. If you want a deeper walk through the SECA mechanics on their own, the Self-Employment Tax calculator isolates that piece; here it is just one of the two inputs feeding your quarterly target.
The safe harbor: the smaller of 90% now or 100%/110% before
Here is the rule that makes this whole tool worthwhile. You do not have to prepay your exact tax to dodge the underpayment penalty — you only have to clear a safe harbor. Two doors lead through it. The first is 90% of what you actually owe this year. The second is your entire tax bill from last year: 100% of it, or 110% if your adjusted gross income last year topped $150,000 (or $75,000 if you file married separately). You are protected the moment you prepay at least one of those amounts. The calculator deliberately aims at the lower of the two, because that is the least cash you can part with and still be penalty-safe. In the example no prior-year figure is entered, so only the current-year door is open: 90% of $18,830.24, which is $16,947.22. That, not the full $18,830.24, becomes the prepayment target. The prior-year door is the one worth understanding, because it is settled before the year even begins. Last year's tax is already filed and unchangeable, so you can divide it cleanly into installments and sidestep the guesswork of projecting the current year. That matters most when your income jumps: if this year is shaping up far richer than last, leaning on 100% (or 110%) of the smaller prior-year number lets you legally defer the extra tax until you file, instead of chasing a moving 90% target every quarter. The 110% step exists so higher earners cannot use a modest prior year to underpay a booming one too aggressively — cross that $150,000 line of prior-year AGI and the bar rises. Enter last year's tax and AGI in the tool, and it picks whichever leg costs you less.
When the balance is too small to bother with: the $1,000 rule
Not everyone who owes at filing has to make estimated payments, and the gate is the $1,000 de minimis rule. The test is narrow and specific: take your projected total tax and subtract only the tax being withheld. If what remains is under $1,000, no estimated payments are required and no underpayment penalty can apply — you simply settle that balance when you file your return. Notice exactly what goes into that subtraction. It is total tax minus withholding, full stop. Estimated payments you have already sent do not enter this particular test; it is built to ask whether withholding alone leaves a trivially small gap. So a contractor with a working spouse whose paycheck withholding nearly covers the household's whole liability may land under the threshold and owe nothing in quarterly installments, even though a few hundred dollars is still due in April. The de minimis exemption forgives the schedule, not the balance. There is a second, cleaner route to the same place. If your tax last year was genuinely zero — you filed a full twelve-month return and owed nothing — the IRS does not ask you to prepay this year at all, regardless of how the current year turns out. The calculator treats a prior-year tax of zero as "not provided" rather than as a real $0 liability, because most people leave the field blank when they simply do not know the figure; if your last return truly showed no tax, you can rely on that exemption directly. Either way, the lesson holds: a small or absent obligation needs no quarterly machinery. The tool signals this by dropping the required estimated payment to nothing and marking your risk as none, so you are never pushed into payments the rules do not demand.
How withholding quietly covers part of the bill — and why its timing is forgiving
Tax withheld from a paycheck is not separate from this plan; it is the first thing credited against it. The required estimated payment is just your safe-harbor target minus whatever is being withheld. If you hold a W-2 job alongside your self-employment, or your spouse does, that withholding can shrink the quarterly figure substantially — and if it covers the target outright, you owe nothing in estimated payments at all. Withholding also carries a quirk that direct payments do not, and it works in your favor. The IRS credits withheld tax as though it came in equal amounts on each of the four installment dates, no matter when it was actually deducted. An estimated payment, by contrast, is stamped with the day you sent it and only protects the quarter it lands in. The practical upshot is a real rescue lever: if you discover late in the year that you have underpaid, raising withholding on a remaining paycheck — or having extra taken from a year-end bonus or a retirement-account distribution — is treated as if it had been spread evenly all year. That can retroactively patch an early shortfall a late estimated payment could never reach. This is why the planner asks for withholding separately from estimated payments already made, and why the two are not interchangeable. Withholding is smeared evenly and can cure the past; dated installments cannot. When you fill in your numbers, use only the federal income tax withheld — the line on your pay stub that says exactly that, not the larger total that bundles in Social Security and Medicare. Overstate the withholding and the tool will understate what you still need to send, which is the quietest way a plan like this goes wrong.
Four deadlines and the arithmetic between them
Federal estimated tax runs on four installment dates: April 15, June 15, September 15, and January 15 of the following year. That last one is the part newcomers miss — the fourth quarter's payment is not due until mid-January, after the calendar year has already closed. The spacing is lopsided too: two months from the first to the second, three to the third, four to the last. These are not tidy three-month blocks, and the IRS does not move them to suit your cash flow. The baseline math is even quarters. Take your required estimated amount and split it into four equal pieces — 25% apiece. In the running example the target is $16,947.22, so each installment is $4,236.80, due on each of the four dates. The calculator shows this flat schedule because sending a clean quarter every period is the simplest way to satisfy the rule. Reality is rarely that clean, so the tool adjusts for where you stand. If you have already made some payments, it subtracts them and spreads only what is left. And if you are planning partway through the year — say you realize in the summer that you owe — it does not pretend the earlier deadlines are still ahead of you. It compresses the full target into the quarters that remain, which means each surviving installment grows. Begin from the third quarter and the same target lands in two payments instead of four, so each one roughly doubles. That is not a penalty; it is simply the same total squeezed into less time. The schedule the calculator prints marks which deadlines have already passed and tells you, in dollars, exactly what to send on each one still to come.
Reading the risk gauge and how a shortfall is actually charged
The underpayment-risk indicator answers one question: if you stopped paying right now, how far short of the safe harbor would you land? It compares what you have already put in — withholding plus any estimated payments made — against the target, and expresses the gap as a share of that target. Fall short by a quarter of the target or less and the gauge reads low; up to three-quarters short reads medium; beyond that, high. When you are already at or past the target, it reads none. Treat these as a measure of exposure, not a probability — the dial is telling you how big the hole is, not the odds of being caught. The penalty behind that gauge is not a flat fine. It behaves like interest on a late loan. For each installment you underpay, the IRS charges a rate it resets every quarter, applied to that quarter's shortfall over the whole stretch it stayed unpaid. Because the clock runs per installment, the damage is cumulative and date-sensitive: a payment you skipped in April keeps accruing right up until you finally cover it or file. That carries a blunt consequence — catching up later shrinks the remaining shortfall but cannot erase the charge already racked up on an earlier quarter you missed. There is no retroactive forgiveness for a deadline that has slipped past. This tool deliberately stops at the risk read-out and does not attach a dollar figure to the penalty, because its purpose is prevention — telling you what to pay so the penalty never starts. If you have already underpaid and want to know what it will actually cost, the companion Estimated Tax Penalty calculator works the Form 2210 arithmetic from your missed installments and their dates.
When income lumps up: windfalls, dry spells, and the annualized option
A steady stream of income makes four equal payments easy. Most self-employment income is not steady, and lumpy earnings are where plans drift off course. Picture a quiet first half followed by a large autumn project, or a one-off event — a capital gain, a Roth conversion, the sale of a property — that lands inside a single quarter. Suddenly the tax you owe for the year is far higher than the early installments assumed. The safe harbor is your shield here. Because a windfall pushes up this year's tax, the 90% door becomes a bigger and more expensive number to clear. The prior-year door, though, does not budge — it was fixed by a return you already filed. So when an unexpected jump hits, anchoring your payments to 100% or 110% of last year's tax lets you stay penalty-safe on a smaller, settled target and pay the extra when you file in April. Re-run the calculator the moment your year changes shape; the recommended quarterly figure is meant to be revisited, not set once in January and forgotten. There is one refinement this tool intentionally does not model. The IRS offers an annualized income installment method — reported on Schedule AI of Form 2210 — that lets you size each installment to the income you had actually earned by that point in the year, rather than assuming it arrived in even slices. For a seasonal business or anyone whose income clusters late, that method can shrink or remove penalties that flat quarters would otherwise impose. This planner uses even quarters for clarity and to keep the recommendation simple; if your income is genuinely front- or back-loaded, treat its schedule as a sound default and know the annualized route exists as a more forgiving alternative when you file.
The mistakes that turn a plan into a penalty
A handful of errors account for most estimated-tax trouble, and each is avoidable once named. The first is budgeting for income tax alone. Self-employment tax is often the larger of the two layers — $11,303.64 against $7,526.60 of income tax in the example — so a plan that omits it can be short by half. Make sure the projected total carries both. The second is assuming withholding makes you exempt. Plenty of people with a W-2 job still owe estimated tax on side income, and unless the leftover balance after withholding sits under $1,000, the quarterly obligation is real. The third is mistaking the safe harbor for the whole bill. Paying 90% keeps you penalty-safe, but the other 10% does not vanish — in the example, $1,883.02 is still due when you file. Set that money aside rather than meeting it as a shock in April. A fourth slip is leaving the prior-year fields blank when last year's tax was actually lower than 90% of this year's. Skip that entry and the tool cannot offer you the cheaper door, so you may prepay more than the rules require. Fifth is bunching all four installments into one late payment, usually in the fourth quarter. Because estimated payments are credited on the date you send them, a December catch-up does nothing for the April, June, and September deadlines that already lapsed — each runs its own clock. Pay each quarter on time instead. Finally, do not forget that a strong year quietly lifts the 90% target as it goes, and that this is a federal calculation only: most states with an income tax run their own estimated-payment system with separate vouchers and dates, and those penalties are assessed independently of anything shown here.
An estimate, not a tax return: what this planner leaves out
Every figure here is a planning estimate, engineered to answer one question — how much to prepay each quarter — not to reproduce a finished return. Several things are left out on purpose, and naming them keeps you from over-trusting the number. The biggest omission is the qualified business income (QBI) deduction, which can lop up to 20% off your self-employment profit before income tax is figured. Dropping it makes this tool's income-tax layer run a little high, which errs on the cautious side for a prepayment plan but overstates your true liability. When you want that deduction folded in, the 1099 Tax calculator builds the full contractor bill including QBI. Three other items sit outside the model as well. The Net Investment Income Tax — an extra 3.8% on investment income once your income clears $200,000 single or $250,000 married-jointly — is not computed here, so heavy investors should add for it separately. The Alternative Minimum Tax is likewise excluded, as is everything at the state and local level: most states levy their own income tax and demand their own estimated payments on their own calendar, entirely apart from this federal plan. The credits field, too, is a single lump for non-refundable credits rather than the full machinery of the child tax credit or any refundable payout. Use the result as a disciplined baseline and refresh it whenever your income, deductions, or payments shift across the year — a plan locked in once tends to drift out of date. And remember that none of this is legal, tax, payroll, accounting, or investment advice. For a complicated year, an unusual credit, a phase-out you are unsure of, or any situation outside the ordinary, check the numbers against the IRS Form 1040-ES instructions or a qualified tax professional before you rely on them.
Frequently asked questions
How much should I pay each quarter?
Your quarterly amount is the safe-harbor target minus tax already withheld, divided by the due dates still left. In the canonical 2026 case — single, $80,000 net self-employment income — total tax is $18,830.24, the 90% safe harbor is $16,947.22, and with no withholding each installment is $4,236.80 across April 15, June 15, September 15, and January 15. The calculator runs this math on your own figures and lays out the schedule. If you've already paid some in, it spreads the remaining balance over the quarters that remain.
What is the safe harbor, in plain terms?
Safe harbor is the IRS's "pay at least this much and we won't penalize you" line. You're protected if your prepayments cover the lesser of 90% of this year's total tax or 100% of last year's total tax — 110% if last year's AGI topped $150,000 ($75,000 if married filing separately). The tool picks whichever number is lower, so you aim at the cheaper target. Clear it and the underpayment penalty disappears, even when a balance remains to settle when you file in April.
What happens if I skip a quarter or underpay one?
Each due date stands on its own. Skip April's installment and the IRS charges interest on that shortfall from April 15 until you make it up — paying double in June shrinks the running penalty but never erases the weeks April sat unpaid. The charge is the IRS underpayment interest rate applied per quarter on Form 2210, not a flat fine. This planner flags the risk before it happens; to size a penalty you've already triggered, turn to the Estimated Tax Penalty Calculator, which models Form 2210 directly.
Do I still owe a penalty if I get a refund at filing?
Possibly, yes. The underpayment penalty is judged quarter by quarter, not by your April outcome. If your money arrived late — most of it bunched into Q4 while earlier installments stayed thin — you can be penalized for those early quarters even though the year ends in a refund. The cure is paying enough on time at each due date, not just enough in total. Withholding is treated as paid evenly all year, which helps; date-specific estimated payments are not. The calculator shows where your timing leaves a gap.
Can withholding replace my estimated payments?
Often, and it's the simpler route. The IRS treats withholding as paid evenly across the year no matter when it actually came out, so a W-2 job, a spouse's paycheck, or withholding on a retirement distribution can cover your safe harbor without four separate mailings. If you have wage income, the Tax Withholding / W-4 Calculator helps you dial up withholding to absorb your self-employment tax. Estimated payments are date-specific and less forgiving on timing. Many people blend both — boost withholding first, then top up with quarterly checks.
What if my income is lumpy or I get a big Q4 windfall?
Even quarterly installments assume steady earnings, which freelancers rarely have. If a windfall lands late in the year, the IRS lets you use the annualized income installment method (Form 2210, Schedule AI) to match payments to when you actually earned — so a December spike isn't treated as owed back in April. This tool sizes the level safe-harbor schedule; for an uneven year, pay more in the quarter the income arrives. Bumping withholding late is another lever, since it's still counted as paid evenly across the year.
What if I owed nothing last year?
A genuinely $0 tax year is a free pass. If your prior-year total tax was zero — and you filed a full 12-month return as a U.S. citizen or resident — you owe no estimated payments this year and face no underpayment penalty, no matter how much you make now. That's the 100%-of-last-year safe harbor at its most generous. You'll still settle the actual bill at filing time. The calculator treats a blank prior-year field as "not provided" rather than a real $0, so if last year truly showed no tax, you can rely on that exemption directly.
Does this include the QBI deduction or my state taxes?
No. To keep the safe-harbor math clean, this planner deliberately leaves out the qualified business income (QBI) deduction, the Net Investment Income Tax, the Alternative Minimum Tax, and all state and local estimated taxes. For the full federal contractor bill with QBI folded in, use the 1099 Tax Calculator. Most states run their own estimated-payment system with separate due dates and safe-harbor rules, so check your state's site. Treat every figure here as a federal estimate to plan around, not your exact final liability.
How is this different from the Self-Employment Tax and 1099 calculators?
They answer different questions. The Self-Employment Tax Calculator computes only the 15.3% SECA tax on your net earnings. The 1099 Tax Calculator builds your whole federal bill — SE tax plus income tax plus the QBI deduction — to tell you what you owe. This Estimated Tax Calculator takes that total and answers when and how much to prepay: it runs the safe-harbor decision, reconciles your withholding and prior payments, and lays out the four-installment schedule. Put simply, the others size the bill; this one keeps you penalty-free while you pay it.
What's the difference between this and the Penalty calculator?
Timing. This tool is preventive — it sizes your quarterly payments before the due dates so you never trigger an underpayment penalty in the first place. The Estimated Tax Penalty Calculator is the after-the-fact tool: once you've already underpaid, it applies the IRS interest rate to each quarter's shortfall on Form 2210 to tell you what the lapse costs. Reach for this planner at the start of the year to set your schedule; reach for the penalty calculator when you've missed installments and need to know the damage.
How do I actually send the money?
You have several free options. IRS Direct Pay pushes a payment straight from a bank account with no account setup. EFTPS (the Electronic Federal Tax Payment System) is the enrolled-account route many self-employed people use to schedule all four installments in advance. You can also mail a paper Form 1040-ES voucher with a check. Card payments work too but carry a processor fee. Whichever you pick, label it for the correct tax year and quarter. The calculator tells you the amount and the date; the IRS handles the transaction itself.
What if I overpay my estimates?
Nothing bad happens to the money — overpaying just hands the IRS an interest-free loan until you file. Any excess becomes your refund, or you can apply it forward to next year's first installment instead of taking cash back. There's no penalty for paying too much; the risk runs only the other way. If your income drops mid-year, lower the later installments rather than overshooting. Re-run the calculator whenever your numbers change so each remaining quarter targets the safe harbor without padding it more than you need to.
Do I owe estimated payments at all — what's the $1,000 rule?
Maybe not. If your total tax minus withholding comes to less than $1,000, the de minimis rule means no estimated payments are required and no penalty applies — you simply pay that small balance at filing. The same holds if withholding alone already covers your safe harbor. So a side gig that nets a few hundred dollars in tax usually needs nothing extra during the year. The calculator checks this threshold first; if you clear it, it tells you to skip the quarterly schedule entirely and settle up in April.