06/12/2026
"I'll just pay it all in April."
This is the most expensive sentence in self-employment.
Q2 estimated taxes are due June 16. Here's what skipping them actually costs:
1️⃣ The underpayment penalty. For 2026, the IRS rate is around 8% annualized. Skip a quarter and the meter starts running on whatever you should have paid.
2️⃣ It compounds. The Q2 amount you skipped accrues interest until you pay it. That's not "next year's problem." That's "today's penalty growing every day."
3️⃣ Safe harbor disappears. Pay 100% of last year's tax (110% if you cleared $150K) and you're protected. Miss it and you owe penalty even if you eventually pay in full.
4️⃣ Stacking quarters. If you skipped Q1 too, the Q2 penalty is added on top. By April, the penalty alone can be $1,500-$4,000 on a $40K tax bill.
5️⃣ The cash flow shock. April hits with a $40K bill plus penalty plus interest, and most owners don't have it sitting in a checking account.
The fix is to pay too much, not too little. Overpaid quarters refund. Underpaid quarters cost.
If you've never run quarterly estimates and your business has grown this year, June 16 is your deadline.
Full breakdown: https://adamtraywick.com/what-happens-if-you-dont-pay-estimated-taxes-2026/
What happens if you don't pay estimated taxes and what to do if you've already missed a quarterly payment in 2026.