Quarterly tax planner

Questions people actually ask

What is the safe harbor for estimated taxes?

The IRS charges no underpayment penalty if your withholding and estimated payments reach the LOWER of two targets: 90% of this year’s tax, or 100% of last year’s tax — 110% if last year’s AGI was over $150,000 ($75,000 married filing separately). This planner computes both on your numbers and tells you which one binds. The practical upshot for a good year: paying based on last year’s smaller tax bill is often perfectly legal and preserves your cash — you just need to budget for the true bill in April.

When are the 2026 quarterly deadlines?

April 15, June 15, and September 15, 2026, then January 15, 2027 — note the uneven gaps: “Q2” covers only two months, which surprises people every year. Each deadline requires the cumulative quarter of your annual target (25%, 50%, 75%, 100%). Miss one and the fix is simple: the planner rolls the shortfall into what to send by the next deadline, because the penalty accrues per day, so paying late is always better than waiting for April.

How is self-employment tax calculated?

On 92.35% of your net profit: 12.4% Social Security up to the 2026 wage base of $184,500 (reduced by any W-2 wages that already used it up), plus 2.9% Medicare on the whole amount, plus 0.9% Additional Medicare above $200,000 ($250,000 joint). Half of the SE tax then deducts from your income before income tax — the planner shows the whole chain with your numbers substituted in.

I also have a W-2 job — do I still owe quarterly taxes?

Maybe not. Your paycheck withholding counts toward safe harbor first, and the IRS treats it as evenly spread across the year no matter when it was withheld — a useful December trick. If your balance after withholding is under $1,000, no estimates are due at all. And often the easiest fix is not vouchers but a new W-4 increasing withholding at your job. The planner nets your withholding out before splitting anything into quarters.

What happens if I skip a payment?

The penalty is essentially interest — currently figured from the federal short-term rate plus three points — on the shortfall, per quarter, from its due date until paid. It is not a cliff, and it is not a reason to panic, but it does accrue daily, which is why the planner’s “to be on track” column includes catch-up: the best moment to fix a missed quarter is the next payment, not next April.

Does this cover state estimated taxes?

No — this plans federal Form 1040-ES only. Most states with an income tax run their own estimated-payment system with similar (but not identical) dates and rules; check your state’s revenue department. It also models the simplified QBI deduction only: if your income is near the QBI phase-out thresholds, or your situation involves capital gains, credits, or multiple businesses, treat this as a planning estimate and confirm the numbers with a tax professional.