Statutory tax guides, filing deadline breakdowns, and deduction rules verified against primary IRS releases.
Calculate your exact 15.3% SE tax, federal bracket liability, standard deduction adjustments ($16,100 single / $32,200 married), and Q1–Q4 quarterly estimated payments.
Every figure sourced to official IRS, SSA, and Treasury documentation.
Deadline-day triage in the order that matters: whether you owe anything at all, the fastest defensible figure if you have not worked one out, the routes whose clocks have already closed, and the one thing to keep once you have paid.
There is no late fee for a missed estimated payment and no notice arriving this week. What starts is interest on that one installment, running per day. What that costs, what still repairs it, and why the next date matters more than the one you missed.
Tuesday takes ten minutes. Monday is the better day to fix the things that made this quarter stressful, and two of them close permanently once the date passes: the withholding lever, and enrolling in EFTPS in time for January.
The underpayment charge is interest, not a fine, so being $3,000 short is a priced decision rather than a failure. Priced out: what the gap costs for 30, 60 and 122 days, and whether putting it on a card is cheaper than owing the IRS.
September 15 is Tuesday. Work through these four questions in sequence and each one can make the next unnecessary — starting with whether you owe a payment at all.
Net rental income is excluded from net earnings from self-employment, so it never meets the 15.3%. It is still income the IRS expects instalments on, and nobody withholds a cent of it. What a landlord pays in September, and the deduction that makes it smaller than the bank statement suggests.
You get 60 days after a layoff to choose COBRA or a Marketplace plan. Walking away from COBRA later does not reopen the Marketplace, so the choice is about a date as much as a price. The window, and why a September quote is the worst one you will see.
The IRS has postponed the Q3 estimated tax payment for taxpayers across Indiana, Michigan, Nebraska, Mississippi, Wisconsin, West Virginia and several more areas, some to November 2 and some to February 1, 2027. Relief is automatic and keyed to your address of record. How to tell whether it reaches you.
There are two defensible ways to size a Q3 estimated payment. One of them is a single line off your 2025 return and three keystrokes. The other is a four-step projection for anyone whose year looks nothing like last year. Both end with the same subtraction.
A high-deductible health plan wins on premiums every year. It only wins on total cost below a specific point. For the plan pair most employers offer, that point sits near $1,700 of care a year, and one line of arithmetic finds yours.
For 2027 the IRS set the HSA contribution limit at $4,500 self-only and $9,000 family. The maximum out-of-pocket a qualifying plan may impose rose by twice as many dollars. What that gap means before you pick a plan in November.
The IRS has published the applicable percentage table for 2027, and it ends at 400 percent of the federal poverty line. One dollar of income past that line does not shrink the credit. It removes it. Here is where the line sits in dollars, and which levers move you back under it.
A capital gain, an RSU vest or one oversized invoice between June 1 and August 31 lands in the third estimated-tax period. When that creates a September 15 payment, when the safe harbor erases it, and the payroll lever that beats writing a check.
Virginia's extended deadline is November 1, Louisiana's is November 15, and Hawaii's is October 20 — all later than the federal date, because their original due dates start later. Delaware's original due date is later too, but its extension snaps back to October 15 anyway.
Filing on time already stopped the ten-times-bigger penalty. A payment plan is the second move: it cuts the failure-to-pay penalty in half and costs as little as $29 to set up. Here is how the numbers actually change once one is in place.
The window to elect a Solo 401(k) deferral for 2025 closed on December 31. What is still open right up to your extended deadline is funding it, funding a SEP-IRA from scratch, and in one specific case, opening a brand-new plan you have never had.
The underpayment penalty is not one penalty. It is four separate calculations, one per quarter, each running from its own due date. Here is what that changes about September 15, and when filing Form 2210 yourself beats letting the IRS bill you.
The simplified method caps out at $1,500 and asks nothing of you. Actual expenses can be worth several times that and ask for a lot. Three realistic situations, run both ways, with the rule that decides each one.
The filing penalty runs at ten times the payment penalty, which is why filing on time matters even when you cannot pay. What has been accruing since April 15, what stops on October 15, and what does not.
Self-employment tax is 15.3%, but not on what you think. It applies to 92.35% of your net profit, stops at a ceiling for the larger half, and half of what you pay comes straight back as a deduction. Here is the whole calculation.
Unemployment compensation is federally taxable income, but no tax comes out of it by default. Here is the one form that fixes it, the flat rate you get, and how to tell whether the September 15 estimated-tax deadline now applies to you.
The underpayment penalty is figured separately for each due date, so catching up on September 15 leaves the April and June shortfalls standing. The annualized income installment method and a W-4 change are the only two mechanisms that reach backwards.
The income was always taxable. What changes when a platform crosses $20,000 and 200 transactions is that the IRS gets a matching document. If you expect to owe $1,000, September 15 is now your date too.
Direct Pay closes its same-day window at 8 p.m. Eastern. EFTPS closes its at 8 p.m. the day before, and enrolling takes a week. What counts as on time is the moment you submit, not the day your bank moves the money.
State estimated tax does not copy the federal calendar. California's third instalment is zero percent. New York starts at $300 of tax, New Jersey at $400, Pennsylvania at $430 — all far below the federal $1,000 line.
The phase-in range that decides whether a service business keeps the deduction is now 50% wider, and there is a new $400 minimum for small operators. Which of the three zones you land in, and the ceiling that catches people before any of it matters.
Pay in the right percentage of your 2025 tax and the IRS cannot charge you an underpayment penalty for 2026, however good this year gets. Which percentage applies to you, and the withholding rule that gives you a second chance in December.
Business miles are worth 72.5 cents through June 30, 2026, then 76 cents from July 1 — how to split your log so each trip is claimed at the right rate.
The 1099-K threshold that briefly dropped to $600 is back to $20,000 and 200 transactions for 2026, and it was never really about whether you owe tax at all.
Which home-office method gets freelancers a bigger 2026 deduction: the $5-per-square-foot simplified option or tracking actual expenses, worked through with real numbers.
Who has to send the IRS a Q3 estimated payment by September 15, 2026, the Safe Harbor rule that gets most filers out of it, and a worked example of what missing the date actually costs.