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The First-Year Startup Tax Checklist (2026)

Every federal and state tax task a new startup owes in year one: EIN, the S-election clock, your first return, payroll, and why domestic firms skip BOI.

By the Acorn 9 teamReviewed by a licensed CPA on the Acorn 9 team

Your startup's first year has a tax to-do list that starts the day you incorporate — long before you have revenue, and often before you have a bank account. Most of it is simple if you do it on time and expensive if you don't. This is the full checklist, branched by how your company is taxed, current for the 2026 filing season.

Start here: the four things every new company does

Regardless of entity type, every startup needs to:

  1. Get a federal EIN. Apply free on IRS.gov immediately after formation. You need it to open a bank account, run payroll, and file anything.
  2. Open a dedicated business bank account. Commingling company and personal money pierces your liability shield and turns bookkeeping into archaeology. Do it before the first transaction.
  3. Know your federal return and its deadline (this depends on entity type — see below).
  4. Handle your home state's annual report and franchise tax (see our state deadline lookup).

The big 2026 change: domestic startups no longer file a BOI report

If you read a startup checklist written in 2024, it almost certainly told you to file a Beneficial Ownership Information (BOI) report with FinCEN within 90 days of formation, under the Corporate Transparency Act. For US-formed companies, that requirement is gone.

In March 2025, FinCEN issued an interim final rule exempting domestic companies entirely. Only foreign entities that register to do business in the US remain in scope. So if you formed a Delaware C-corp or a California LLC, you have no BOI filing to make. The interactive checklist below marks this as exempt so you can stop worrying about a deadline that no longer applies to you.

Branch by entity type

How your company is taxed drives your return and your deadlines. Pick your type in the tool below — it computes your S-election deadline from your formation date and lists the tasks that actually apply to you.

Interactive

First-year tax checklist

How is your company taxed?
  • Get a federal EINRight after formation

    Apply free on IRS.gov, immediately after formation. You need it to open a bank account, run payroll, and file.

  • Open a dedicated business bank accountBefore first transaction

    Separating company and personal money protects liability limits and makes bookkeeping (and our job) far cleaner.

  • File federal income tax return — Form 1120April 15, 2026 (calendar-year)

    C-corps file Form 1120 for the prior calendar year. A 6-month extension (Form 7004) moves the filing date, not the payment date.

  • Beneficial Ownership (BOI / CTA) reportNo filing required (domestic)

    EXEMPT for you. Under FinCEN's March 2025 interim final rule, domestic US companies no longer file a BOI report. Only foreign entities registering to do business in the US remain in scope.

  • Pay quarterly estimated taxesQuarterly

    C-corps owing $500+ pay corporate estimates (Apr/Jun/Sep/Dec). Pass-through owners pay personal estimates on their share of profit (Apr 15 / Jun 15 / Sep 15 / Jan 15).

  • Set up payroll if you pay wagesBefore first paycheck

    If owners or employees draw a salary, register for payroll tax accounts and file employment returns (941/940). S-corp owner-employees must take reasonable W-2 compensation.

  • Capture startup costs & the R&D creditAt first return

    Deduct up to $5,000 of startup costs in year one (the rest amortizes). If you have US R&D payroll, a qualified small business can apply the R&D credit against payroll tax — see our R&D credit guide.

  • File your state annual report & franchise taxVaries by state

    Every state of formation or registration has its own report and (often) a franchise/annual tax — Delaware C-corps owe franchise tax by March 1. Use our state deadline lookup.

A starting checklist for the most common cases as of the 2026 filing season — not exhaustive and not tax advice. Deadlines that fall on a weekend or holiday roll to the next business day. Confirm your specific obligations with a CPA.

C-corporation (the venture-backed default)

  • Form 1120, due April 15 for a calendar-year company.
  • The C-corp is a separate taxpayer — it pays corporate income tax on profit, and shareholders are taxed again on dividends.
  • Pay quarterly corporate estimates if you expect to owe $500+.
  • This is the standard structure for startups raising venture capital: institutional investors require it, and QSBS (the up-to-$15M capital-gains exclusion) is only available on C-corp stock.

S-corporation (file Form 2553 — on the clock)

  • Requires a timely Form 2553 election: within 2 months and 15 days of formation to apply in year one.
  • Form 1120-S, due March 16, 2026 (the 15th is a Sunday). Issues K-1s to shareholders.
  • Owner-employees must take reasonable W-2 compensation before taking distributions — the IRS scrutinizes zero-salary S-corps.

Multi-member LLC (partnership)

  • Form 1065, due March 16, 2026. Issues K-1s to members.
  • The LLC itself usually pays no federal income tax; members pay on their share via personal estimates.

Single-member LLC (disregarded)

  • No separate federal entity return — business income flows onto your personal Form 1040, Schedule C, due April 15, 2026.
  • You still need an EIN for payroll and banking, and you still owe state annual reports and franchise tax.

Don't forget these

  • Payroll, done right. The moment anyone — including a founder — draws a salary, you must register for payroll-tax accounts and file employment returns (941/940). For S-corps this is non-optional.
  • Quarterly estimated taxes. C-corps pay corporate estimates; pass-through owners pay personal estimates (roughly Apr 15 / Jun 15 / Sep 15 / Jan 15). Skipping them invites penalties even if you pay in full at filing.
  • Startup costs and the R&D credit. You can deduct up to $5,000 of startup costs in year one (the rest amortizes over 15 years). If you have US-based R&D payroll, a qualified small business can apply the R&D credit against payroll tax — see our R&D tax credit guide.
  • State obligations stack. Your state of formation has an annual report and often a franchise/annual tax (Delaware C-corps owe franchise tax by March 1). If you operate in other states — including via a remote employee — you may have to register and file there too. See our multi-state nexus guide.

A loss year is not a no-filing year

Most pre-revenue startups assume that "we made no money" means "we don't file." That is wrong, and it is costly. Filing a return in a loss year:

  • Preserves your net operating loss (NOL) to offset future profit.
  • Starts the clock on IRS audit statutes.
  • Keeps your entity in good standing for the next financing.

The cost of filing a clean zero/loss return is small. The cost of an unfiled return, a blown S-election, or a missed franchise tax — penalties, lost elections, a corp in bad standing during diligence — is not.

Bottom line

The first-year list is short and mostly mechanical: EIN, bank account, the right federal return on the right date, the S-election clock if you want S status, payroll if you pay anyone, estimates if you owe, and your state filings. Domestic companies can cross BOI off entirely. Run the checklist above against your formation date, then confirm the specifics with a CPA before your first deadline — not after.

This guide is informational only and is not tax advice. Deadlines reflect the 2026 filing season for calendar-year entities; weekend/holiday deadlines roll to the next business day. Sources: IRS Form 1120 / 1120-S / 1065 / 2553 instructions · FinCEN interim final rule, March 2025 (BOI domestic exemption) · IRC §195 (startup costs) · Rev. Proc. 2013-30 (late S-election relief). Reviewed by a licensed CPA on the Acorn 9 team.

FAQ

Frequently asked questions

What taxes does a startup owe in its first year?
Even pre-revenue, a new company has obligations: get an EIN, file a federal income tax return for its entity type (Form 1120 for a C-corp, 1120-S for an S-corp, 1065 for a multi-member LLC, or Schedule C on the owner's 1040 for a single-member LLC), pay any state franchise/annual tax and file the state annual report, run payroll correctly if anyone draws a salary, and pay quarterly estimated taxes if it owes them. A loss year still usually requires a return — and filing one preserves the net operating loss.
Does my startup have to file a BOI (beneficial ownership) report?
If it is a US-formed company: no, not anymore. Under FinCEN's interim final rule issued in March 2025, domestic companies are exempt from the Corporate Transparency Act's Beneficial Ownership Information reporting. Only entities formed outside the US that register to do business in the US remain in scope. This reverses the 2024 guidance, so older checklists telling you to file a BOI report within 90 days are out of date for domestic startups.
When is the Form 2553 S-corp election deadline?
To have S-corp tax treatment apply for your first tax year, file Form 2553 within 2 months and 15 days of formation (roughly the 15th day of the third month). Miss that window and S status generally takes effect the following year, though the IRS grants late-election relief in many cases under Rev. Proc. 2013-30. The interactive checklist computes the exact date from your formation date.
When is my startup's first tax return due?
For a calendar-year company filing 2025 returns in 2026: C-corp Form 1120 is due April 15, 2026; S-corp Form 1120-S and partnership Form 1065 are due March 16, 2026 (the 15th is a Sunday); a single-member LLC reports on the owner's Form 1040, due April 15, 2026. A six-month extension (Form 7004 / 4868) moves the filing date but not the payment date — tax owed is still due in spring.
Do I need to pay estimated taxes in year one?
A C-corp that expects to owe $500 or more must pay quarterly corporate estimates. For pass-through entities (S-corp, partnership, single-member LLC), the company itself usually owes no federal income tax, but the owners pay personal quarterly estimates on their share of the profit. Underpaying triggers penalties even if you settle up at filing, so set this up early.
What's the difference between a C-corp and an LLC for taxes?
A C-corp is a separate taxpayer: it files Form 1120 and pays corporate tax on its profit, and shareholders pay again on dividends. An LLC is taxed by default as a pass-through — a single-member LLC is disregarded (reported on the owner's return), and a multi-member LLC files a partnership return — so profit is taxed once, on the owners' returns. C-corp status is standard for venture-backed startups because investors and QSBS require it; LLCs are common for bootstrapped or services businesses.