A startup founder estimates quarterly tax payments by projecting full-year income, deductions, credits, income tax and self-employment tax, then paying that total in four installments. Founders with little or no withholding generally must pay this way if they expect to owe at least $1,000 in federal tax after withholding and credits, according to the Internal Revenue Service in IRS estimated taxes guidance.
Estimated tax is pay-as-you-go tax for income without withholding. It covers sole proprietors, partners and S-corporation shareholders. It prevents a large April bill and keeps payments current as income arrives.
Table of Contents
- Do you need to pay quarterly?
- How do you calculate each installment?
- When are payments due?
- How do you avoid an underpayment penalty?
- How do you pay and stay documented?
Do you need to pay quarterly?
Most founders do when startup income has no withholding. Salary withholding covers only wages, not founder draws, distributions or side income. If expected tax after withholding and credits reaches $1,000, quarterly payments apply.
Net self-employment earnings of $400 or more trigger self-employment tax. That tax is 15.3%, with 12.4% for Social Security and 2.9% for Medicare, according to the Internal Revenue Service in IRS Understanding Taxes tutorial. Founders figure it on Schedule SE and report it on Form 1040.
How do you calculate each installment?
Start with last year's return, then adjust for this year's reality. Project adjusted gross income, taxable income, deductions and credits.
Add income tax plus self-employment tax for the year. Use the Form 1040-ES worksheet to turn that projection into installments. Divide the yearly total into four payments, then adjust later quarters when income changes.
- Pull prior-year income, deductions and credits as a baseline.
- Add expected founder income, subtract planned deductions.
- Calculate income tax and self-employment tax on the new totals.
- Subtract expected withholding, then divide the balance by four.
When are payments due?
Federal payments fall on April 15, June 15, September 15 and January 15 of the next year, according to the Internal Revenue Service in IRS estimated-tax FAQs. The gaps are uneven, so June and September can arrive fast. Mark all four dates before the year starts.
A weekend or legal holiday moves the deadline to the next business day. That rule makes a payment timely, not late. Keep bank confirmation for each date.
How do you avoid an underpayment penalty?
Meet a safe harbor through timely withholding plus estimates. The Internal Revenue Service describes coverage of 90% of current-year tax or 100% of prior-year tax in its IRS pay-as-you-go guide. The prior-year target rises to 110% when prior-year adjusted gross income exceeded $150,000, or $75,000 for married filing separately.
Startup income is often lumpy, so re-estimate every quarter. A strong second quarter may require larger June and September payments. The annualized-income method can help when most profit arrives late in the year.
How do you pay and stay documented?
Pay online through IRS Direct Pay, EFTPS or an IRS Online Account, by phone, or by mailing Form 1040-ES vouchers. Choose one method per quarter and save the receipt. Report all estimated payments on Form 1040.
Paying too little or paying late can trigger a penalty as interest on each quarterly shortfall. The charge can apply even if the founder later pays in full or receives a refund. Uneven income should be re-estimated quarterly to limit that risk.