Safe Harbor Won’t Save You in April
THE Q2 ESTIMATED TAX DEADLINE IS MONDAY, JUNE 15.
Most business owners will pay their safe harbor, feel covered, and get a surprise next April. Safe harbor protects you from penalties. It does nothing about the balance.
Those are not the same thing.
The clearest way to see it: win the billion-dollar Powerball tomorrow and you'd owe your safe harbor across the four quarters. The rest of the tax waits until April, penalty-free.
A big business year works the same way - a deal closes early, a launch overperforms - you pay your safe harbor in quarterlies and settle the balance in April.
You're not winning the Powerball. But plenty of you are having the big year. Here's what to check before you send Monday's payment.
The rule, in 30 seconds
If you expect to owe at least $1,000 for 2026 after withholding and credits, the IRS wants quarterly payments. Sole proprietors, single-member LLCs, S-Corp owners, anyone whose business income lands on a personal return.
The dates: April 15, June 15, September 15, January 15. Underpay and you owe a penalty on top of the tax.
Safe harbor is the escape hatch. Hit one of these across the four payments and the IRS cannot charge a penalty, no matter what you earn:
- 100% of your 2025 total tax (Form 1040, Line 24) if your 2025 AGI was $150,000 or less.
- 110% of that number if your 2025 AGI was over $150,000.
- Or 90% of your 2026 tax as you earn it. The current-year method.
The IRS doesn't send a reminder. The penalty is the reminder.
That's where most coverage of this stops. It's the wrong place to stop, because safe harbor says nothing about what you'll owe in April.
The one move before Monday: Pull your YTD P&L through May. Project the full year. Compare that number to your safe-harbor number. Everything below is how to read the result.
WHICH SITUATION ARE YOU IN?
Your income is up. This is the common one.
Married S-Corp owner. $100K salary. Last year: $220K income, $25K total tax. Your 110% safe harbor is $27,500, or $6,875 a quarter. You've been paying it. You're penalty-proof.
But you're on track for $350K this year, and your 2026 federal tax lands around $49,000. (Assumes MFJ, the $100K salary, the QBI deduction, no state tax.)
Safe harbor got $27,500 in the door. The bill is $49,000. That's a $21,500 check due April 15 - the same day your Q1 2027 estimate is due.
The question was never penalties. It's whether you have $21,500 set aside. If not, start now. Hold 30-35% of monthly profit in a separate tax account, on top of what your quarterlies cover.
Don't prepay the extra to the IRS. Keep your money until April and send their number, not a dollar more.
YOUR INCOME IS DOWN. 25% OR MORE BELOW LAST YEAR.
Prior-year safe harbor is now working against you.
Married S-Corp owner. Last year: $300K income, $40K tax. Your 110% safe harbor is $44,000, or $11,000 a quarter. But business slowed, and you're tracking $150K this year, about $12,000 in 2026 tax. (Same assumptions: MFJ, QBI, no state.)
Pay the $44,000 safe harbor and you've handed the IRS $32,000 it owes back to you next spring. That's $32,000 out of your business for ten months, doing nothing.
Switch to the current-year method. Project full-year tax, take 90%, divide by four, and base June 15 on that number instead of last year's return. If you overpaid Q1, credit it forward and your June payment shrinks further.
THE S-CORP TRAP
A lot of S-Corp owners think payroll has their taxes handled. Payroll handles the tax on your salary. It does nothing about your K-1.
Your W-2 wages have withholding. Your K-1 profit has none. That piece runs through estimates, and it's where owners come up short - especially if revenue climbed since January and your salary didn't. An owner with $100K in wages and $250K in K-1 profit has a big estimate gap payroll never touches.
Two ways to close it. Bump your June 15 estimate. Or raise your salary for the rest of the year so more tax runs through withholding.
Here's why the second one is good: withholding counts as paid evenly across the entire year, no matter when it comes out of your check. Withhold extra in Q4 and the IRS treats it as if you'd paid it in equal pieces since January. A late salary bump can cure a shortfall from earlier quarters that an estimate can't. It moves your payroll tax too, so model it before you touch anything.
Before Monday: pull your YTD withholding, project your full-year K-1, and confirm withholding plus estimates clears your safe-harbor number.
A SIDEBAR FOR LUMPY INCOME
One more, for the keen. If your income lands late in the year - slow spring, heavy fourth quarter - the equal-quarters default makes you overpay early. There's a method (Schedule AI on Form 2210) that bases each payment on what you'd earned by that date instead. You keep cash in the business through the slow months and stay penalty-free.
It's fiddly, it's all-or-nothing for the year, and it runs at filing. If your income is back-loaded, reply and we'll run it for you.
WHERE YOU STAND
Within 10% of last year: send what you sent in April. Safe harbor is doing its job.
Down 25% or more: drop June 15 to 90% of your revised full-year estimate. Get the projection first.
Up 25% or more: pay the prior-year safe harbor on June 15, then move the extra into your reserve, not the voucher. Know your April number today.
All three start the same way. A real projection off your actual YTD numbers through May. Not last year's figure. Not a guess.
One thing this doesn't cover: your state. Most states run their own June 15 estimate with their own safe harbor. If you're in a tax state, check that number too.
WHAT WE DO AT VISOR
This is the exact work we do with every client every quarter. YTD review, full-year projection, safe-harbor check, April reserve target.
You have until Monday. Book a call and we'll give you all three numbers today - your payment, your reserve, and your April balance.
P.S. Missed the April 15 payment? The penalty on Q1 is running. A clean June 15 payment won't erase it, but it stops the later quarters from piling on. Form 2210 shows exactly where you stand. Worth knowing before you file.