Glossary · Tax & Accounting
Quarterly Estimated Taxes (1040-ES).
Federal estimated tax payments due quarterly (April, June, September, January) for self-employed taxpayers including owner-operators.
What it is
Quarterly estimated taxes are federal tax payments due four times per year for self-employed taxpayers — and for W-2 earners with substantial under-withheld additional income. The 2026 due dates are April 15, June 15, September 15, and January 15 of the following year. Payments are filed on IRS Form 1040-ES. The calculation includes both federal income tax and self-employment tax (15.3% combined Social Security and Medicare).
The IRS safe-harbor rule lets a taxpayer avoid underpayment penalty by paying 100% of the prior year's total tax (110% if AGI was over $150K). Underpayment penalty in 2026 runs at roughly 8% annualized interest, calculated quarter-by-quarter on the shortfall. State estimated taxes are due on a parallel schedule for most states with an income tax. Owner-operators new to self-employment routinely underestimate the combined federal-plus-SE-plus-state burden in their first year.
Why it matters for trucking finance
Owner-operators who fail to pay quarterly often face $2,000–$5,000+ in penalties at year-end. The 15.3% self-employment tax catches first-year operators off guard — it's on top of federal income tax. Calendar these dates. Many operators set up a separate "tax savings" bank account funded monthly at 25–30% of net income to cover the quarterly payments. Underestimated taxes drain working capital and can force operators into MCA or working-capital loans to bridge the cash crunch — turning a $4,000 tax shortfall into a $5,500 borrowing cost.
Related terms
- Self-Employment Tax (SE Tax) — 15.3% federal tax on net self-employment income (12.4% Social Security + 2.9% Medicare); paid by sole proprietors, partners, and LLC owner-operators.
- Schedule C — IRS Form 1040 Schedule C — Profit or Loss from Business; used by sole-proprietor owner-operators to report business revenue, expenses, and net profit.
- 1099-NEC — IRS Form 1099-NEC reports non-employee compensation paid to independent contractors; brokers issue 1099-NEC to carriers who received $600+ in a year.
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