Tax deadlines requirements: an account-by-account audit

Nobody sends you a tax calendar. Every filing hangs on an account, a registration or an identifier you already hold, and each one keeps creating duties until you close it.

Start from the accounts, not from the dates. The list of accounts is the list of your filing requirements. The IRS publishes the federal due dates, and in California three state bodies publish the rest.

What to take away

The accounts, the forms and how often they fall due

Read the table from the left. If you hold the account, the form in the third column is yours, on the rhythm in the fourth, whether or not anyone reminds you.

Where a local gross receipts tax exists, a finance department or tax commission at city or county level publishes it. Local layers vary the most, which is why the license row has no single date. Ask the city or county office that issued it when the renewal falls due.

Federal due-date rules, from IRS Publication 509

The IRS gathers its federal due dates in Publication 509 (2026), Tax Calendars. Its dates are written as rules tied to the end of a tax year or a quarter, so you can apply them to your own year.

The EIN comes first. The IRS says to use Form SS-4 to apply for an employer identification number, a 9-digit number assigned to employers, sole proprietors, corporations, partnerships and other entities for tax filing and reporting purposes. Every federal date below hangs on it.

How the business is taxed decides the return. A sole proprietor files Schedule C with Form 1040, a partnership files Form 1065, an S corporation files Form 1120-S, and a C corporation files Form 1120. That question is settled in entity tax treatment before it becomes a calendar question.

Form 1065 is due on the 15th day of the 3rd month after the end of the partnership's tax year. Form 1120-S is due on the 15th day of the 3rd month after the end of the corporation's tax year. Form 1120 is due on the 15th day of the 4th month after the end of the corporation's tax year.

Asking for more time to file is a separate request, made on Form 7004 for the partnership, S corporation and C corporation returns. Payroll does not wait for it. Employees create deposit and reporting schedules that run on their own clock, and those schedules do not slow down because a return was extended.

Your Form 941 is due by the last day of the month that follows the end of the quarter. Form 940, the Employer's Annual Federal Unemployment (FUTA) Tax Return, is due the last day of the first calendar month after the calendar year ends. Both are employer returns, so they arrive with the first payroll.

A state example: three California agencies, three calendars

California splits the state layer three ways. The EDD runs payroll and unemployment, the CDTFA runs sales and use tax, and the Secretary of State keeps the entity registration. Income and franchise tax sit with the Franchise Tax Board, a fourth body.

The payroll account comes first for any employer. You must file both the Quarterly Contribution Return and Report of Wages (DE 9) and its continuation, the DE 9C, each quarter. The DE 9 reconciles reported wages and paid taxes, and the DE 9C reports individual employee wages. The EDD requires these returns and payroll tax deposits electronically.

The EDD's 2026 payroll tax calendar shows the DE 9 and DE 9C for the 3rd quarter of 2026 (July, August, September) due October 1, delinquent if not filed by November 2, 2026. The 4th quarter of 2026 falls due January 1, 2027, delinquent if not filed by February 1, 2027.

The seller's permit runs on a frequency you do not choose. The CDTFA assigns a filing frequency (quarterly prepay, quarterly, monthly, fiscal yearly, yearly) based on your reported sales tax or your anticipated taxable sales at registration. A filing is required on or before the due date, even if there are no sales to report.

For the July to September quarter, the filing period ends September 30 and the quarterly return is due October 31. If a due date falls on a weekend or state holiday, it moves to the next business day. Sales tax attaches to transactions, not profit, so a business can owe it in a month it lost money.

The entity registration is the third calendar. Statements of Information are filed online at bizfileOnline. After the initial statement, later ones fall due in a statutory 6-month filing window set by the month of incorporation, registration, formation or conversion. Failure to file may bring Franchise Tax Board penalties and suspension or forfeiture.

Effective August 1, 2026, web User Access is required for Statement of Information filings. Any time your information changes between statutory filing periods, the Secretary of State says an updated statement should be filed. Both points catch an entity that changes officers or its address mid-cycle.

Other states split the work differently. In Texas, the Comptroller of Public Accounts publishes the state tax calendar while the Texas Workforce Commission runs unemployment insurance. The IRS keeps a directory of state government websites with information on doing business in the state, taxation and links for employers.

What a hire or a new state adds

Obligations follow where work is physically performed, not where the company is registered. One remote hire in another state can add a withholding account and an unemployment account there.

Registering, hiring, holding inventory or maintaining an office in a state usually brings that state's calendar with it. Each new account goes on the list with its own form and rhythm. A first employee in California, for example, brings the DE 9 and DE 9C every quarter alongside the federal Form 941.

Closing an account is its own task

Each account rests on an identifier. The IRS issues an EIN for the business, and the state agency that administers unemployment or withholding issues its own account number. Those numbers are what keep a filing obligation alive.

A quiet period still needs a filing, generally, while a registration is open. The CDTFA says so directly for sales tax returns. Closing a registration you no longer need is worth doing on purpose, and a state agency's own page says how.

An account audit you can run this week

Rebuild the list once a year from the agencies' own pages, then work from your copy and read every agency letter the week it arrives. How to tell a real date change from a misquoted one is covered in tax deadline rules.

Why the account list matters for deductions and mileage

For deductions and mileage claims, deadlines set the tax year those items land in. A mileage log and the receipts behind a deduction only help if they reach the right return on time.

An extension can move the filing date for a return, but it does not move a payment date. That is why the account list comes before the receipts: it tells you which returns, in which states, those records have to support.

If you track business miles, the date you file is also the date you need your log complete enough to support the standard mileage rate or actual expense method. Build the account list first, then match each deduction and mileage record to the year it belongs to. The state business tax overview covers the state side of that match.

Common questions

How do I know I have found every obligation?

Start with the identifiers you hold, then map each one to a filing. Then have a CPA check that list against your facts, because the lines people miss are the ones they did not know to look for.

Nothing changed in my business. Do I still rebuild the calendar?

Yes, briefly. Your business did not change, but the published dates and the rules behind them can.

Does a quiet period still need a filing?

Generally yes, while a registration is open. That is why closing registrations you no longer need is worth doing on purpose.

Can my accountant just hand me the calendar?

They can hand you the part they handle. Ask what they do not handle, then find out who does. That gap is where missed obligations live.