Startup Tax Filing: A Founder's Calendar of Federal and State Deadlines

Startup tax filing is less about any single April date and more about a year that never really stops. A US startup owes returns, payments, and information forms to the IRS, to Delaware, and to one or more state tax agencies, and those obligations land in almost every month. Miss one and the penalty is rarely fatal, but it is avoidable, and the interest compounds while you are heads down shipping the product.

This guide lays the year out as a calendar so you can see what is due and roughly when. Treat the dates as a map, not a guarantee. Exact deadlines shift when a due date falls on a weekend or a legal holiday, they depend on your entity type, and they assume a calendar tax year. A fiscal-year company counts months from its own year end instead. When you need the authoritative version, the IRS publishes a quarter-by-quarter tax calendar that supersedes any summary, including this one. This post is general information, not tax or legal advice.

How Your Entity Type Sets the Calendar

Before any date matters, the entity decides which return you file and when. Most venture-backed startups are Delaware C corporations, but plenty of early companies run as LLCs or operate through partnerships, and the deadlines differ.

C corporation: files Form 1120. For a calendar-year company the return is due the 15th day of the fourth month after year end, which is April 15. A six-month extension moves the filing deadline to October 15, though any tax owed is still due in April.

S corporation: files Form 1120-S and issues a Schedule K-1 to each shareholder. The return is due the 15th day of the third month, March 15, with an extension to September 15.

Partnership or multi-member LLC: taxed as a partnership files Form 1065 and issues K-1s to the partners. It shares the March 15 deadline and the September 15 extension.

Single-member LLC: with one owner is usually disregarded, so its activity flows onto the owner's personal return on the April 15 individual timeline unless it has elected corporate treatment.

Almost every other date below hangs off this choice, so pin down your entity and your year end first.

Federal Income Tax Return Deadlines

The income tax return is the anchor of startup tax filing, and the month depends entirely on the entity from the previous section. Two spring dates cover most companies.

March 15: is the pass-through deadline. S corporations and partnerships file, and their K-1s go out so owners can finish their own returns. If your investors are waiting on a K-1, this is the date they care about.

April 15: is the C corporation and individual deadline. Form 1120 is due, and so are the personal returns of founders and pass-through owners.

Extensions: buy time to file, not time to pay. Filing Form 7004 pushes a business return to September 15 for pass-throughs or October 15 for C corps, but the IRS still expects the tax itself by the original date.

A pre-revenue startup with losses still files. There is no income to tax, but the return preserves net operating losses to carry forward, starts the clock on the statute of limitations, and keeps the company in good standing with the IRS.

Estimated Quarterly Taxes

If the company or its owners owe tax for the year, the IRS wants it in installments rather than one lump sum, and it charges an underpayment penalty when the installments fall short. Most early startups running at a loss owe nothing here, but a profitable company or a founder taking distributions needs the dates.

Individual estimates: for founders and pass-through owners fall on April 15, June 15, September 15, and January 15 of the following year. These cover the tax on income that has no withholding, such as a K-1 share of partnership profit.

Corporate estimates: for a calendar-year C corp fall on April 15, June 15, September 15, and December 15. The fourth installment lands in December, not January, which trips up teams that assume it mirrors the individual schedule.

Safe harbors: let you avoid the penalty by paying a set percentage of last year's tax or the current year's, whichever the rules allow for your situation. A startup with a first profitable year should check the thresholds rather than guess.

Payroll Taxes: Deposits and Forms

The moment a startup runs payroll, a second and stricter cadence begins. Payroll tax is money you withheld from employees plus the employer share, and the IRS treats late deposits harshly because the funds are not really yours to hold.

Deposits: follow a monthly or semiweekly schedule the IRS assigns based on your prior payroll volume. A monthly depositor remits by the 15th of the following month. Most startups use a payroll provider that moves these on time, but the legal responsibility stays with the company.

Form 941: is the quarterly payroll return, due at the end of the month after each quarter: April 30, July 31, October 31, and January 31. It reconciles wages paid and taxes withheld for the quarter.

Form 940: reports federal unemployment tax once a year and is due January 31.

W-2s: go to employees and to the Social Security Administration by January 31, so wage reporting for the prior year is largely a January exercise.

1099 Issuance to Contractors

Startups lean on contractors, and paying them creates an information-reporting duty separate from any income tax. The workhorse form is the 1099-NEC for nonemployee compensation.

Who gets one: is generally any unincorporated contractor or vendor you paid $600 or more during the year for services. Collect a Form W-9 from every contractor before you pay them so you have the taxpayer ID when January arrives.

January 31: is the deadline to send the 1099-NEC to the recipient and file it with the IRS. It is one of the earliest and easiest deadlines to miss because it arrives right as the year turns.

Payment method matters: because payments made through a card or a third-party network are reported by that processor on a 1099-K, so you do not double-report them on a 1099-NEC. Clean books make this distinction obvious instead of a January guessing game.

Delaware Franchise Tax and Annual Report

A Delaware entity owes Delaware something every year regardless of where it operates or whether it earned a dollar, and this is separate from income tax. The Delaware Division of Corporations handles these filings and payments.

Corporations: file an annual report and pay franchise tax by March 1. Delaware offers two calculation methods, and the default authorized-shares method can produce an alarming number for a startup with millions of authorized shares. The assumed-par-value-capital method usually yields a far smaller bill, so it is worth computing both.

LLCs, LPs, and general partnerships: do not file an annual report but owe a flat annual tax due June 1.

Good standing: depends on staying current. Miss the deadline and Delaware adds a penalty plus interest, and a lapsed entity can lose good standing, which investors and banks check during diligence.

State Income, Franchise, and Sales Taxes

Home states, or offices, or employees in several states, layer another set of obligations on top of the federal and Delaware ones. There is no single national deadline here because each state runs its own agency and its own dates.

State income tax: returns often track the federal calendar but not always, and a company with employees or property in multiple states may have nexus and a filing duty in each. Remote hires quietly create these obligations.

State franchise or business taxes: exist in many states as a charge for the privilege of doing business there, distinct from income tax and owed even in a loss year.

Sales tax: applies where you sell taxable goods or services and have a nexus, which for online sellers can be triggered by economic activity in a state even without a physical presence. Sales tax filing frequency varies from monthly to annually depending on volume, and the money is collected from customers and held in trust for the state.

The practical takeaway is to map where you have people, property, and customers, then confirm each state's obligations directly.

R&D Credit and Elections at a High Level

Not every tax event is a bill. The research and development credit rewards qualified spending on developing or improving products and software, which describes most of what an early engineering team does. A pre-revenue startup can often benefit even without income tax to offset.

The payroll offset: lets a qualified small business elect to apply part of the R&D credit against the employer share of payroll taxes rather than income tax, so a company with losses still gets cash value. The election is made on the timely filed return, which ties this back to your March or April deadline.

Documentation: is the price of the credit. You need to substantiate the qualifying activities and costs, so track engineering time and project scope during the year rather than reconstruct it later.

Other elections: such as accounting method choices and entity elections also attach to the return and often cannot be made late, which is one more reason the annual filing is a decision point, not just a formality. Confirm the current rules and dollar limits, which change, against the IRS guidance before you rely on any figure.

How Meow's Back Office Handles Filings

Keeping this calendar straight while running a company is exactly the kind of work a founder should hand off. Meow's back office covers end-to-end federal and state income tax filings for US startups, along with bookkeeping, so the returns are prepared from clean numbers rather than a year-end scramble.

Income tax filings: run end to end, federal and state, so the C corp or pass-through return and the state returns are handled together instead of stitched across separate providers.

Bookkeeping underneath: keeps the ledger current all year, which is what makes a filing fast and a credit like R&D defensible. Meow's books sync and reconcile with QuickBooks and Xero, so the financials a preparer needs are already in order.

One back office: means bookkeeping, tax, and related work run off the same account and the same numbers, rather than three vendors reconciling to each other after the fact. The 409A valuation many startups need for option grants lives in the same place.

Meow does not remove your responsibility to know your obligations, and it does not replace a tax adviser in a genuinely complex position. It removes the manual assembly and the missed-date risk that comes from tracking a dozen deadlines by hand.

Frequently Asked Questions

When are startup tax returns due? For a calendar-year company, S corporations and partnerships file by March 15, and C corporations and individuals file by April 15. A timely extension moves the filing deadline to September 15 for pass-throughs or October 15 for C corps, but any tax owed is still due on the original date. Fiscal-year companies count from their own year end, and dates that fall on a weekend or holiday shift to the next business day.

Does a startup with no revenue still have to file? Yes. A pre-revenue company with losses still files its income tax return, its payroll and information forms if it has employees or contractors, and its Delaware franchise tax and annual report. Filing preserves net operating losses to carry forward, keeps the entity in good standing, and starts the statute of limitations. Skipping it creates penalties even when no tax is owed.

What is Delaware franchise tax and when is it due? Delaware franchise tax is an annual charge for being a Delaware entity, separate from income tax and owed regardless of revenue. Corporations file an annual report and pay by March 1, while LLCs, LPs, and general partnerships owe a flat annual tax by June 1. Corporations can compute the tax two ways, and the assumed-par-value-capital method usually costs far less than the default authorized-shares method.

When do 1099s and W-2s have to go out? Both are due January 31. Send a 1099-NEC to any unincorporated contractor you paid $600 or more for services during the year and file it with the IRS, and send W-2s to employees and to the Social Security Administration. Collect a W-9 from each contractor before paying them so you have the taxpayer information ready in January.

What are estimated quarterly taxes and who owes them? Estimated taxes are installment payments on income that is not subject to withholding, and they apply to profitable companies and to owners taking distributions. Individuals pay on April 15, June 15, September 15, and January 15, while a calendar-year C corp pays on April 15, June 15, September 15, and December 15. Paying too little across the year triggers an underpayment penalty.

Does Meow file startup taxes? Yes. Meow's back office covers end-to-end federal and state income tax filings for US startups, plus bookkeeping that keeps the ledger current and reconciled with QuickBooks and Xero. Running the books and the filings off the same account means the return is prepared from clean numbers rather than a year-end reconstruction. This is general information, not tax or legal advice.

A Note on Meow

Meow does not pretend the tax year is simpler than it is. The calendar has a dozen moving dates because the tax code has a dozen moving parts, and the value is in keeping them all tracked and filed from one place. Meow's back office handles end-to-end federal and state income tax filings and the bookkeeping that feeds them, syncs with QuickBooks and Xero, and sits alongside 409A valuations and bill payments, so a founder tracks the business instead of the deadlines.

File on Time, Every Time

Print the calendar, or better, hand it to a back office that runs it for you. Know your entity, mark the federal and Delaware dates, confirm your state obligations, and keep the books current so filing is a review rather than a rebuild. This is general information, not tax or legal advice. Learn more at meow.com.

Meow Technologies is a financial technology company, not a bank or FDIC-insured depository institution. Banking services are provided by Grasshopper Bank, N.A.; Member FDIC. The FDIC's deposit insurance coverage only protects against the failure of an FDIC-insured bank.