Owner-Operator Quarterly Taxes: How Much to Pay and When

Nobody withholds tax from an owner-operator's settlements. So the IRS expects you to pay during the year, in four estimated payments. Skip them and you can owe a penalty on top of a big bill in April. Here's how to work out what to send.

The two taxes you owe

• Self-employment (SE) tax. This is Social Security and Medicare for people who work for themselves. It's 12.4% for Social Security plus 2.9% for Medicare, figured on 92.35% of your net profit. For 2026, the Social Security part only applies to the first $184,500 of earnings, less any W-2 wages you had. Half of your SE tax is deducted before income tax.
• Federal income tax. This uses the regular brackets (10% up to 37%) on your taxable income, after the standard deduction and, for most owner-operators, the qualified business income (QBI) deduction.

If your earnings pass $200,000 single or $250,000 married filing jointly, a 0.9% Additional Medicare Tax applies to the part over that line.

2026 numbers you need

• Standard deduction: $16,100 single or married filing separately, $24,150 head of household, $32,200 married filing jointly.
• Single brackets: 10% up to $12,400, 12% to $50,400, 22% to $105,700, 24% to $201,775, 32% to $256,225, 35% to $640,600, and 37% above that. The joint brackets are twice as wide at the low end: 10% up to $24,800 and 12% to $100,800.
• QBI deduction: up to 20% of qualified business income, but no more than 20% of taxable income. The simple version works when taxable income is at or under $201,750 ($403,500 married filing jointly).

Worked example

A single owner-operator expects $85,000 of profit on Schedule C for 2026, before per diem. She was out 200 full days and 50 partial days, so her per diem deduction is $15,200 (see the per diem guide).

1. Profit after per diem: $85,000 − $15,200 = $69,800.
2. Net earnings for SE tax: $69,800 × 92.35% = $64,460.30.
3. Social Security: $64,460.30 × 12.4% = $7,993.08.
4. Medicare: $64,460.30 × 2.9% = $1,869.35.
5. SE tax: $7,993.08 + $1,869.35 = $9,862.43. Half of it, $4,931.22, is deductible.
6. Adjusted gross income: $69,800 − $4,931.22 = $64,868.78.
7. After the $16,100 standard deduction: $48,768.78.
8. QBI deduction: QBI is $69,800 − $4,931.22 = $64,868.78, and 20% of that is $12,973.76. But 20% of taxable income is only $9,753.76, so the deduction is $9,753.76.
9. Taxable income: $48,768.78 − $9,753.76 = $39,015.02.
10. Income tax: 10% of $12,400 = $1,240, plus 12% of the $26,615.02 above that = $3,193.80. Total $4,433.80.
11. Total federal tax: $4,433.80 + $9,862.43 = $14,296.23.

Spread over four payments, that's about $3,574 a quarter. Notice that SE tax is more than double the income tax here. That's normal for owner-operators in the lower brackets, and it's why deductions like per diem matter: every dollar off your profit cuts both taxes.

If she had only sent $3,000 each in April, June, and September, she'd have $14,296.23 − $9,000 = $5,296.23 left for the January payment. The quarterly tax estimator does this catch-up math for you.

When to pay

For tax year 2026, the four 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 by February 1, 2027 and pay everything you owe with it.

How much is enough to avoid a penalty

You generally avoid the underpayment penalty if your withholding and estimated payments add up to the smaller of 90% of your 2026 tax, or 100% of your 2025 tax (110% if your 2025 adjusted gross income was over $150,000, or $75,000 if married filing separately). Paying last year's tax is the safe choice in a year when you don't know how much you'll make. Paying 90% of this year's estimate keeps more cash in the truck when business is down.

Tips from the numbers

• Set money aside every settlement. In the example, tax is about 20% of total income. Moving that share into a separate account each week beats scrambling in September.
• Update the estimate each quarter. A slow first half or a big repair changes your profit. Re-run the numbers before each due date and adjust the rest of the payments.
• Know your profit. The estimate is only as good as the profit number you put in. The P&L generator and cost per mile calculator help you get it right.

This is an estimate. It leaves out credits, state tax, health insurance and retirement deductions, and special cases above the QBI threshold. A tax pro can fine-tune it.