Estimated taxes when income is lumpy

Salaried households experience tax as withholding: the employer remits, April brings a small balance or refund, and life continues. Households with uneven income experience tax as a timing problem. Income arrives in large pieces: a business sale, an RSU vest, a bonus, a carried interest distribution, a trust distribution, a large rebalancing gain, or K-1 income with no cash attached. The federal and state systems still expect payment during the year. Miss the timing and the result is underpayment penalties, a cash shortfall in April, or a forced sale to cover a bill that could have been planned.

This post covers how estimated taxes work for the 2026 tax year, the safe harbors, and a quarterly routine for households with more than one income stream. It is not a voucher calculator. It is the routine that makes your preparer's calculation useful.

What estimated taxes are for

Estimated taxes are prepayments for income that has no withholding, or not enough. If you expect to owe $1,000 or more after withholding and credits, the IRS expects quarterly payments. That covers anyone whose wages are a small part of the tax picture, and anyone whose wages are large but whose equity and investment events are larger.

For the 2026 tax year, federal payments are due:

• April 15, 2026
• June 15, 2026
• September 15, 2026
• January 15, 2027

You can skip the January payment if you file your 2026 return and pay the full balance by February 1, 2027 (January 31 falls on a Sunday). Most states run parallel systems with their own thresholds and dates. Paying federal estimates and ignoring the states is one of the most common misses.

Taxable income and cash do not move together

A distribution arrives in March and gets spent. Estimates are based on last year's quieter numbers. A September K-1 shows taxable income with no matching cash. January requires a large payment. Taxable income builds a liability during the year. Cash arrives on its own schedule. Your projection needs to track both.

The safe harbors

You generally avoid the federal underpayment penalty if your withholding plus timely estimates equal at least the smaller of:

• 90% of your 2026 tax, or
• 100% of your 2025 tax, rising to 110% if your 2025 AGI was more than $150,000 ($75,000 if married filing separately).

The prior-year safe harbor needs a full 12-month prior-year return. Most households in this post will be on the 110% figure.

What each tool is good for:

• Prior-year safe harbor: a planning floor when this year's income could jump in ways you cannot forecast. It is a known number in January.
• Annualized installment method: when income is heavily concentrated late in the year, Form 2210 Schedule AI lets required payments follow when income was actually earned. It takes careful worksheets.
• Withholding: federal wage withholding is treated as paid evenly through the year, even if it happens in December, unless you elect otherwise. Increasing withholding on a late-year bonus or an IRA distribution can cover an earlier shortfall. Use it with your preparer, not from a social media tip.

The safe harbor prevents the penalty. It does not prevent a large balance due in April if this year's tax is much higher than last year's. Avoiding the penalty and having the cash are separate problems.

The penalty is interest-based. The IRS underpayment rate is 7% a year, compounded daily, for the fourth quarter of 2026. It resets quarterly.

Five kinds of lumpy income

• Type A, known date and uncertain amount: formula bonuses, carried interest tied to a scheduled close.
• Type B, known amount and flexible date: securities sales you control.
• Type C, fixed date and fixed amount: RSU vests, option expirations, note maturities.
• Type D, late and opaque: K-1s that arrive near September 15 with surprises.
• Type E, multi-state: income sourced to a state with its own estimate rules.

Each needs a different approach. Type B lets you pair the sale with a payment. Type C needs a scheduled top-up before the vest. Type D calls for the prior-year floor plus a cushion. Type E needs a state-by-state table, not one federal number.

A quarterly routine

• Early January: Make the final payment for the prior year. Build a first projection for the current year. Confirm the safe harbor target. Adjust W-4s for anyone on payroll.
• Before April 15: Update for first-quarter events. Set state payments. Run a high case and a low case.
• Before June 15: Add spring bonuses and known closings. Decide whether annualization fits.
• Before September 15: Add summer events. Ask fund sponsors for K-1 estimates. Raise cash for the extended return if needed.
• Before January 15: Final catch-up with the best available numbers, coordinated with any year-end withholding.

Name who updates the projection, who approves the payment, and who confirms it posted. Missed dates usually come from unclear ownership, not from bad math.

Equity compensation

RSUs are ordinary income when they vest. Employers usually withhold federal tax at the flat 22% supplemental rate, and at a mandatory 37% on supplemental wages above $1 million for the year. If your marginal rate plus state tax is higher, the difference is yours to pay through estimates or extra withholding. Social Security stops at the 2026 wage base of $184,500, but the 0.9% Additional Medicare Tax applies above $200,000 of wages (employers withhold it at that level regardless of filing status).

For each material vest, write a three-line card before the date: taxable income created, withholding expected, and the top-up needed. Put the top-up on the calendar like any other bill.

Incentive stock options and the alternative minimum tax are outside this post. For 2026 the AMT exemption is $140,200 for joint filers and begins phasing out at $1,000,000 of AMT income ($90,100 and $500,000 for single filers). Raise ISO exercises with your preparer before you exercise.

Sale years

A business sale or large capital gain produces a wire that feels like after-tax money. It is not. Escrow holdbacks, earnouts, and purchase-price adjustments change the final gain later. Estimate with a conservative gain figure, update when the closing statement is final, and hold the tax in a separate account.

Long-term gains face up to 20% federal tax, plus the 3.8% net investment income tax when modified AGI exceeds $250,000 for joint filers or $200,000 for single filers. Those NIIT thresholds are not indexed for inflation, so more households cross them each year.

K-1 income without cash

You owe tax on your share of partnership or S corporation income whether or not the entity distributes cash. If a large share of your income comes through K-1s, use the prior-year floor and revise upward mid-year once sponsors publish estimates.

Charitable gifts and your estimates

Large gifts can lower your tax and your required payments, but only once they are completed and substantiated in the right year. Pledges do not count. Non-cash gifts need appraisals. For 2026, itemizers deduct only gifts above 0.5% of AGI, and the benefit of itemized deductions is capped at 35% for those in the 37% bracket. Do not reduce a payment based on a gift that has not happened.

States

State rules differ on thresholds, safe harbors, annualization, and nonresidents. A nonresident with one large gain sourced to a state may owe that state an estimate even when the federal safe harbor is met. Part-year residency years are the hardest. Add a state tab to the projection. If you have nonresident wage exposure or more than one home state, build those calendars into it.

A tax reserve account

Open a separate account titled for taxes. Move money in when income arrives: a set percentage of each distribution, a fixed amount after each vest, a transfer after each large gain. Keep it in cash or short-term instruments that will be available on the due date. Write down the withdrawal rule: tax payments only.

Some households borrow against securities to pay tax rather than sell. That can be reasonable. If it happens every April, the estimate process is not working.

Prepayments from more than one source

Two careers, director fees, trust withholding, composite returns filed by entities, and an overpayment applied from last year can all count as prepayments. Keep one ledger of every source and reconcile it to your IRS account transcript each year. This is how households avoid both underpaying and forgetting a credit they already have.

Scored diagnostic

Score each question 0, 1, or 2. Total possible: 24.

#	Question	Score
1	Is there a current-year projection updated at least quarterly?
2	Does it show federal and each material state separately?
3	Are vest and bonus dates in it?
4	Are K-1 figures based on sponsor estimates plus a cushion?
5	Is the prior-year safe harbor figure checked each January?
6	Are federal and state due dates on a shared calendar?
7	Is each payment confirmed as posted?
8	Is withholding coordinated with estimates?
9	Does every large sale get a tax estimate before closing?
10	Is there a separate tax reserve account?
11	Were penalties in the last three years reviewed for their cause?
12	Could someone else find and update the projection file?

Below 14 means the payment schedule is reacting to events rather than planned around them.

Illustrative examples

Illustrative: An executive has $4 million of RSU income across four vest dates. Withholding at 22% and 37% trails the household's combined federal and state rate. No top-ups are made. April becomes a borrowing decision. The fix is a vest card and a scheduled payment for each date.

Illustrative: A founder receives a large sale wire and spends part of it before estimating the tax. The final payment arrives with a penalty and requires selling securities in a down market. A reserve account opened on closing day would have prevented both.

Illustrative: A household on the 110% prior-year safe harbor avoids the penalty but still owes a large balance because K-1 income doubled. The safe harbor worked. The cash plan did not. They add a September check with sponsors.

What to tell your preparer each quarter

• Sales or distributions closed or likely
• Changes to vest or bonus schedules
• Large charitable gifts planned for this year
• Changes in where you live or work
• New fund commitments that will issue K-1s
• Payroll withholding changes
• Marriage, divorce, or a move

A November meeting

Forty-five minutes in November: payments to date against the safe harbor, remaining vests and closings, K-1 risk, the state table, the reserve balance against the projected balance due, and a written decision on the January payment. Write the decision down with an owner and a date.

Common failure modes

• Dividing last year's tax by four every year without checking
• Ignoring state estimates
• Spending a sale wire before setting aside the tax
• Assuming RSU withholding covers the full tax
• No one owns the projection
• Learning a due date from a penalty notice

Uneven income is normal for many households. A missed payment is a scheduling problem, and it has a scheduling fix: a projection updated each quarter, a reserve account, and due dates on the calendar before the next large payment arrives.

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Educational only. This is not tax or legal advice for your situation. Consult your own CPA, EA, or attorney before acting.