On Line 7 of Form 4868, enter the amount you’re paying with your extension request. That figure should equal your estimated balance due from Line 6, which is your estimated total tax for the year (Line 4) minus what you’ve already paid through withholding and estimated payments (Line 5). If you can’t cover the full Line 6 balance, pay as much as you can. The extension pushes back your filing deadline by six months, but it does not push back your payment deadline, so anything left unpaid after April 15 starts accruing interest and penalties right away.
You aren’t required to send a payment for the extension to be valid. The form’s instructions are explicit on that point. But entering $0 on Line 7 when you owe a real balance is usually the wrong call, because the failure-to-pay penalty and interest begin the day after the original due date regardless of whether your extension went through.
How Line 7 Connects to Lines 4, 5, and 6
The form runs in a short sequence. Line 4 is your best estimate of total tax liability for the year. Line 5 is total payments already made toward that liability. Line 6 subtracts Line 5 from Line 4 to give you the estimated balance due. Line 7 is what you actually choose to send.1Internal Revenue Service. Form 4868 – Application for Automatic Extension of Time To File U.S. Individual Income Tax Return
To get the automatic extension, three things have to happen: you properly estimate your tax liability, you enter that estimate on Line 4, and you file Form 4868 by the original due date.1Internal Revenue Service. Form 4868 – Application for Automatic Extension of Time To File U.S. Individual Income Tax Return The Line 7 payment is separate from those requirements, but the number you put there depends entirely on how carefully you handled Lines 4 and 5.
Getting Line 4 Right
Line 4 is where most of the work goes, because everything downstream flows from it. The IRS wants a good-faith estimate, not a precise figure, and there are two workable approaches.
The simpler path is to start with last year’s return. Pull the “Total Tax” line from your most recent Form 1040 and adjust for what changed. If your wages went up by $25,000 and you’re in the 22% bracket, add roughly $5,500. If you sold a home or cashed out investments, add the expected capital gains tax. If you lost a major deduction or credit, factor that in. You’re approximating, not preparing a final return.
If your situation changed a lot, build the estimate from current-year documents instead: final pay stub, 1099s, records of investment income, and so on. Subtract the standard deduction (for 2025, $15,750 single, $31,500 married filing jointly, $23,625 head of household2Internal Revenue Service. New and Enhanced Deductions for Individuals) or your estimated itemized deductions, then apply the IRS rate schedules.
Line 4 is total tax, not just income tax. If you had freelance or business income, add self-employment tax at 15.3% of net earnings (12.4% Social Security up to the annual wage base, plus 2.9% Medicare).3Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes) Higher earners should also add the 3.8% Net Investment Income Tax, which applies when modified AGI tops $200,000 single or $250,000 married filing jointly, on the lesser of net investment income or the amount over that threshold.4Internal Revenue Service. Net Investment Income Tax
Adding Up Line 5
Line 5 is the total you’ve already paid toward the year’s tax. The instructions point to the amount you expect to report on Form 1040, Line 33.1Internal Revenue Service. Form 4868 – Application for Automatic Extension of Time To File U.S. Individual Income Tax Return That includes federal income tax withheld from wages and any 1099s, quarterly estimated payments made on Form 1040-ES, and refundable credits you expect to claim (such as the Earned Income Tax Credit or the refundable portion of the Child Tax Credit).
Undercounting Line 5 is a common mistake. A forgotten quarterly payment or withholding from a side gig can inflate your Line 6 balance and push you into overpaying on Line 7. Add up every payment source before moving on.
Deciding What to Actually Put on Line 7
Line 6 is arithmetic: Line 4 minus Line 5. If the result is zero or negative, you can enter $0 on Line 7. If it’s positive, that’s your estimated balance, and the ideal Line 7 amount equals that balance.
If you can’t pay the full balance, work backward from a safe harbor. You avoid the separate underpayment penalty (a different rule from the failure-to-pay penalty) if your total payments for the year meet any of these thresholds:5Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual To Pay Estimated Income Tax
- 90% of your current-year tax.
- 100% of the tax shown on your prior-year return, which is the easiest target to hit because the number is already known.
- 110% of prior-year tax if your prior-year AGI was above $150,000 ($75,000 if married filing separately).
- Balance under $1,000 after subtracting withholding and refundable credits: no underpayment penalty regardless of the percentages.
To use a safe harbor as your Line 7 floor, take the target dollar figure, subtract Line 5, and pay at least that difference. If last year’s total tax was $12,000 and you weren’t above the high-earner threshold, getting your total payments to $12,000 protects you from the underpayment penalty even if your actual liability ends up much higher.
There is no minimum payment for the extension itself to be valid. But paying nothing when you clearly owe is a gamble, and paying a token amount when you owe a lot doesn’t buy much protection either.
What Underpaying Costs
Two penalties can hit, plus interest, and they work independently.
The failure-to-pay penalty is 0.5% of the unpaid balance for each month or partial month it stays unpaid, capped at 25%.6Office of the Law Revision Counsel. 26 USC 6651 – Failure To File Tax Return or To Pay Tax Filing an extension does not reduce this rate. It runs from the original April deadline until you pay in full or hit the cap.
The failure-to-file penalty is 5% per month, also capped at 25%.7Internal Revenue Service. Failure to File Penalty A valid extension protects you from this one through the extended October deadline. Here’s the catch that matters for Line 4 and, by extension, Line 7: if the IRS decides your Line 4 estimate grossly understated your actual liability without a reasonable explanation, it can void the extension retroactively, and the 5% penalty applies as if you never filed for one.8Internal Revenue Service. IRM 20.1.2 Failure To File/Failure To Pay Penalties “Grossly understated” is a high bar, but entering $0 on Line 4 when you know you earned six figures is the kind of move that draws it.
Interest accrues daily on any unpaid tax from the original due date until paid, at the federal short-term rate plus 3 percentage points, adjusted quarterly.9Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026 There’s no cap, and it compounds daily. That’s the main reason to make Line 7 as large as you reasonably can.
How to Send the Line 7 Payment
For 2025 returns, the deadline is April 15, 2026. If you e-file, the date and time in your time zone when the return is transmitted determines timeliness.10Internal Revenue Service. Topic No. 301, When, How and Where to File
The cleanest option is IRS Direct Pay from a checking or savings account, at no cost; select “Extension” as the payment type.11Internal Revenue Service. Direct Pay With Bank Account If you e-file Form 4868 through tax software, you can authorize an Electronic Funds Withdrawal so the extension and payment go through together. EFTPS is also free but takes a few days to enroll if you don’t already have an account.
Card payments go through approved third-party processors. Debit runs about $2.10 to $2.15 per transaction; credit is roughly 1.75% to 1.85% of the amount. None of the fee goes to the IRS.12Internal Revenue Service. Pay Your Taxes by Debit or Credit Card or Digital Wallet
Making an electronic payment and selecting the extension payment type automatically counts as filing for the extension, so you don’t have to send Form 4868 separately.
Paying by check or money order works too. Write your name, address, daytime phone, Social Security number, the tax year, and “Form 4868” on the check, and mail it with the form to the address listed in the instructions for your state.13Internal Revenue Service. Pay by Check or Money Order Give the mail extra lead time; the postmark date is the filing date.
If Your Estimate Was Off
If Line 7 came in above your final liability, you claim the overpayment on your actual return. You can take it as a refund or apply it to next year’s estimated taxes. The IRS does not refund the excess based on the extension alone; you have to file the return.
If your final tax turns out higher than Line 4, you owe the difference plus interest and any failure-to-pay penalty that accrued on the shortfall from April 15 forward. File and pay as soon as you can to stop the meter. There is no separate penalty for estimating incorrectly, as long as your original estimate was made in good faith and wasn’t wildly off from reality.