Founders taxed as individuals face quarterly deadlines of April 15, June 15, September 15, and January 15 of the following year. Calendar-year C-corporation startups face April 15, June 15, September 15, and December 15 of the same tax year.
Quarterly estimated payments are pay-as-you-go prepayments of income tax. They cover business income that has no employer withholding. The right deadline turns on entity type, not company size.
Official resources:
- Read the official guidance from Irs — Use this primary source to verify the official guidance.
- Read the official guidance from Irs — Use this primary source to verify the official guidance.
Table of Contents
- Which deadline fits your startup?
- What are the 2026 individual dates?
- Do you owe estimated tax at all?
- Why does timing matter more than equal quarters?
Which deadline fits your startup?
Sole proprietors, partners, and S-corporation shareholders generally follow the individual schedule. According to the Internal Revenue Service pay-as-you-go guide, those payments fall on April 15, June 15, September 15, and January 15 of the following year IRS pay-as-you-go guide. Calendar-year C corporations use a different fourth date. According to Internal Revenue Service Publication 542, their installments are due April 15, June 15, September 15, and December 15 of the same tax year IRS Publication 542 on corporations.
A corporation on a fiscal year pays on the 15th day of the 4th, 6th, 9th, and 12th months of its fiscal year. Check formation papers and tax election before marking a calendar. An LLC taxed as a partnership follows the individual dates. The same LLC taxed as a C corporation follows the corporate dates.
What are the 2026 individual dates?
For 2026 income, the individual pattern means April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027. Each date covers a successive slice of 2026 income. Early-year profit is paid first, late-year profit is paid last.
A founder with steady freelance revenue can plan four similar payments. A founder with a midyear launch or funding event should tie each payment to income already received. Timing follows earnings, not incorporation date.
Do you owe estimated tax at all?
Not every startup must pay each quarter. According to the Internal Revenue Service estimated-taxes page, individuals generally must pay when they expect to owe at least $1,000 after withholding IRS estimated taxes page for small businesses. Corporations generally must pay when they expect at least $500 of tax liability. A pre-revenue team with little taxable income may fall below those lines.
A profitable consultancy, agency, or app with early sales can cross them fast. Review expected tax after withholding each quarter. Founders with both wages and startup income should count both streams. Higher salary withholding can reduce the amount due by estimate. Lower withholding leaves more to prepay.
Why does timing matter more than equal quarters?
The IRS payment periods are unequal. According to the Internal Revenue Service underpayment penalty page, for example, January 1-March 31 is longer than April 1-May 31 IRS underpayment penalty page for individuals. Payments should match when income was received rather than being four equal calendar quarters. That structure punishes catch-up payments.
The Taxpayer Advocate explains that missing a period can trigger an underpayment penalty even if the startup later gets a refund. Taxes operate pay-as-you-go during the year. Seasonal founders should track income by period. A large Q1 contract calls for an April payment. A quiet spring followed by strong fall sales shifts weight toward September and January.
- Calculate each period from actual income received to date.
- Send the April, June, September, and January amounts on their own deadlines.
- Use Form 1040-ES, an IRS online account, Direct Pay, or EFTPS for individual payments.
- For a C corporation, deposit electronically and use the Form 1120 worksheet formerly called Form 1120-W.