The deadlines this calendar covers
The calendar applies the published rules for each kind of business to the details you enter. It does not store what you type, and it covers the filings most small companies owned by founders abroad must make. It does not cover payroll, sales tax returns or filings that depend on events, such as a change of director.
US LLCs owned by a non-US person
A single-member LLC owned by a foreign person is treated as a "foreign-owned US disregarded entity". It must file Form 5472 with a pro forma Form 1120 by the 15th day of the fourth month after its tax year ends, which is 15 April for a calendar year. Form 7004 extends the filing date to 15 October if it is filed by the original deadline. The IRS penalty for not filing is $25,000 per form, and a foreign-owned disregarded entity cannot e-file these forms, so they go by fax or mail. The filing can be required even in a year with no income, because money the owner puts into the LLC or takes out counts as a reportable transaction.
US C corporations
A corporation files Form 1120 by the 15th day of the fourth month after its year end, with a Form 7004 extension to the 15th day of the tenth month. The federal rate is 21%.
State filings
Wyoming LLCs file an annual report and pay the license tax on the first day of their anniversary month. Delaware LLCs pay a $400 annual tax on 1 June (from the 2026 tax year) and Delaware corporations file their annual report and franchise tax by 1 March. Florida annual reports are due between 1 January and 1 May, and Texas franchise tax reports are due on 15 May. New Mexico LLCs have no annual report. The calendar covers all 50 states and Washington DC: it adds each state's annual or biennial report (or its annual tax, such as California's $800 LLC tax) using the due-date rule the state publishes, and shows nothing for states with no yearly LLC filing, such as Arizona, Missouri, Ohio and South Carolina. A few states tie the due date to your own record (Colorado's periodic report month and New Jersey's annual report date); for those the calendar sets a reminder at the end of your formation month and tells you to check the date on your state record. The LLC fees by state table lists every rule with its official source. Every state requires a registered agent, so the calendar also shows the agent renewal on your formation anniversary when you enter a formation date.
UK private limited companies
Every UK company files a confirmation statement at least once every 12 months, within 14 days after the end of its review period. The fee is £50 online. The calendar uses your incorporation anniversary as the review date.
Annual accounts go to Companies House 9 months after the accounting reference date, except the first accounts, which are due 21 months after incorporation. The first accounting reference date is the last day of the month in which the first anniversary of incorporation falls, which is why the calendar defaults a UK year end to the end of your incorporation month. Late accounts cost between £150 and £1,500 for a private company, doubled if you are late two years running.
Corporation tax is paid 9 months and 1 day after the end of the accounting period for companies with profits up to £1.5 million. The Company Tax Return (CT600) is due 12 months after the end of the period, even when there is no tax to pay. For returns due on or after 1 April 2026 the late filing penalty is £200, with another £200 at three months. HMRC's free filing service closed on 31 March 2026, so returns now go through commercial software.
A VAT-registered business files a VAT return one calendar month and 7 days after the end of each VAT period, usually quarterly, even when nothing is owed. Enter the end date of any one of your VAT quarters and the calendar shows the next return.
UK sole traders
Sole traders file a Self Assessment return online and pay by 31 January after the end of the tax year. If you are new to Self Assessment, register by 5 October after the tax year in which you started. Payments on account, due on 31 January and 31 July, apply when last year's bill was £1,000 or more.
What the calendar cannot know
Rules change and some depend on your records: a shortened or extended accounting period, a changed confirmation statement review date, a Wyoming license tax above the $60 minimum, franchise tax above the Texas threshold, or an IRS extension you already filed. Use the dates as a planning aid, check each official source, and ask a licensed professional when a filing depends on your own tax position.