Before You Touch the Form

Pull together what you have, even if it's incompleteLast year's return, W-2s/1099s you've received, and a rough total of income and deductions. You're estimating, not finalizing.
Estimate your 2025 tax liability as honestly as you canForm 4868 requires you to properly estimate your tax liability and enter your total tax liability on line 4. A lowball guess can cost you later.
Check whether you actually need the form at all if due a refundIf you're due a refund, there's technically no penalty for filing late, but you should still file the extension if you're not sure, since guessing wrong on a refund is risky.

File the Extension Itself

Submit Form 4868 by today, the regular filing deadlineRequest an extension by the April tax filing due date — this gives you until October 15 to file without penalties.
Pick one of the three accepted ways to request itPay all or part of your estimated income tax due and indicate that the payment is for an extension, file Form 4868 electronically via IRS e-file, or file a paper Form 4868 and enclose payment.
Note that no approval or confirmation letter is neededThe extension is automatic once you've properly filed it; just keep your confirmation number or mailing receipt as proof.
Ask your preparer or tax software to e-file the extension today if using paid preparer or softwareDon't assume it happens automatically.
Get your paper Form 4868 postmarked today if filing paper form by mailA late postmark means a late extension request.

Pay your estimated tax by today regardless of the extensionMake sure you pay any tax you owe by the April filing date — the extension is only for filing your return.
Pay at least 90% of your actual tax liability today to avoid the failure-to-pay penaltyAn extension to file a return is not an extension to pay; the IRS will assess the failure-to-pay penalty on any unpaid taxes unless 90 percent of the tax liability was paid by the April deadline.
Understand the cost of underpayingThe failure-to-pay penalty is typically around 0.5% per month, up to a 25% cap of the unpaid amount, plus interest — much cheaper than the failure-to-file penalty, which is why the extension is still worth doing even if you can't pay in full.
Pay online directly and skip the paper form entirely if that's easierTaxpayers can complete and submit Form 4868 electronically, regardless of income, and pay online and select "extension." Taxpayers who pay all or part of what they owe this way don't need to file a separate form.
Pay as much as you can today and set up an IRS online payment plan afterward if cant pay full estimatePartial payment still reduces the penalty and interest that accrue.

Save your confirmation somewhere you won't lose it before OctoberElectronic acknowledgment or certified mail receipt.
Mark October 15 as your new hard deadlineDon't let the extension turn into "forget about it" — the failure-to-file penalty is steep if you miss that date too.
Check your state's rules separately if you owe state taxes if owe state taxesA federal extension doesn't automatically extend your state filing or payment deadline everywhere.
Remember your first 2026 quarterly estimated payment may be due soon after if self employed or no withholdingDon't let the extension distract you from that separate deadline.
Use the extra months to actually finish the returnGather any missing documents and file for real well before October 15, since waiting until the last minute again just repeats today's scramble.