When Are Dormant Company Accounts Due? Deadlines and Late Filing Penalties

By Ben Davies · Updated 5 October 2026

Every UK limited company — dormant or not — has a hard filing deadline baked into its incorporation date. Miss it and the penalties start automatically, with no warning letter and no grace period.

This guide tells you exactly when your dormant accounts are due, what HMRC and Companies House charge if you're late, and what to do if a deadline has already passed. If you'd rather skip the maths, our free dormant deadline calculator will work out all three of your filing dates from your incorporation date or accounting reference date (ARD — the date your accounts are made up to each year).

The headline numbers: 9 months and 12 months

There are two filings a dormant company usually needs to make each year, and they have two different deadlines.

Companies House dormant accounts are due 9 months after your accounting reference date (ARD). If your ARD is 31 December 2025, your accounts must reach Companies House by 30 September 2026. This applies to every subsequent year too — once your ARD is set, the 9-month clock runs from it every year.

HMRC's CT600 corporation tax return is due 12 months after the end of your accounting period. So a 31 December 2025 year-end means the CT600 must be filed by 31 December 2026. A CT600 is due when HMRC sends a notice to deliver one, and once a notice has arrived, a dormant company still has to answer it with a nil return.

Two filings, two deadlines, two different regulators. People miss this all the time — filing the Companies House accounts and assuming HMRC is handled. It isn't.

If you want a full walkthrough of both filings, see our guide on how to file dormant company accounts and the broader dormant company filing deadlines reference.

How to find your accounting reference date

Your ARD is the last day of your company's financial year. For most companies it's set automatically to the last day of the month your company was incorporated in. A company incorporated on 14 March 2025 will get an ARD of 31 March by default.

You can confirm it without hunting for it: run our free Companies House audit on the company number. It reads the public record and tells you when the next accounts are due, and whether anything is already overdue. For any year after the first, the ARD is nine months before that due date.

If you've never changed it, your ARD repeats every year. If you want a deeper explanation, see what is an accounting reference date.

The 31 December dormant company deadline

A huge proportion of UK companies — particularly those incorporated to hold a brand, a domain, or to ring-fence a future project — have a 31 March ARD, giving them a 31 December dormant company deadline for their Companies House accounts. December is one of the busiest months for dormant filings, and Companies House gets hammered with last-minute submissions. Filing in November is much less stressful than filing on New Year's Eve.

First-year companies: the 21-month rule

Newly incorporated companies get a longer first deadline because their first accounting period is usually longer than a year.

For a brand-new company, the first set of accounts is due 21 months after the date of incorporation. So if you incorporated on 10 May 2025, your first dormant accounts are due by 10 February 2027.

After that first filing, you switch to the standard 9-month rule running from your ARD.

There are some quirks here — the first accounting period can be up to 18 months long, and HMRC's rules sometimes carve that into two periods for CT600 purposes. We cover the detail in first year filing for a new company.

Companies House late filing penalties

Companies House penalties are automatic. There is no warning, and the penalty applies even if the company has never traded a penny. You can appeal one if you have good grounds.

The amount depends on how late you are:

If you're already overdue, plug your dates into the free late filing penalty calculator to see exactly which band you're in.

Two things catch people out here:

• The penalty doubles if you filed late in the previous year too. So a £150 penalty becomes £300 the second time. A £1,500 penalty becomes £3,000. Repeat offenders are punished hard.
• The clock runs to the date Companies House receives the accounts, not the date you sent them. Accounts that arrive a day late are late.

If the company is more than six months late and you take no action, Companies House will eventually begin proceedings to strike the company off the register. That's a separate process from the penalty, and it can wipe out anything held in the company's name.

For more detail, see what are Companies House late filing penalties and our deep dive on late filing penalties.

HMRC penalties for a late CT600

HMRC's penalty regime is completely separate. You can be on time with Companies House and still get hit by HMRC, or vice versa.

For a late CT600:

• 1 day late: £200 flat penalty.
• 3 months late: another £200, so £400 total.
• 6 months late: HMRC estimates your tax bill ("determination") and adds a 10% penalty on top of the estimated tax.
• 12 months late: another 10% penalty on the estimated tax.

For a dormant company that genuinely owes no tax, the determination penalty is usually £0 — but the two £200 fixed penalties still apply — doubled from £100 for returns due on or after 1 April 2026, with the old rate still running for anything that fell due before then — and they're charged in addition to anything Companies House charges. The fixed penalties are higher again if a return is the third late one in a row.

The cleanest fix is always to file the nil CT600 before HMRC issues a determination, because once they've made one, you have to formally displace it by filing the actual return.

What to do if you're already late

Don't ignore it. Filing now won't cancel a penalty already due, but it stops it moving into a higher band — and the strike-off risk gets real after six months.

The steps are usually:

1. Pull your most recent confirmation statement and check what was last filed for both Companies House and HMRC.
2. Prepare and file the missing dormant accounts immediately — every day matters because the penalty bands jump at the 1-month, 3-month, and 6-month marks.
3. File any missing CT600s for periods HMRC has sent a notice for, oldest first. HMRC will accept multiple nil returns at once.
4. Deal with any penalty notice you receive — appealing rarely works for "I forgot," but it can succeed for genuine reasons such as bereavement or serious illness. Photograph the notice and we check it for grounds against your filing record and the register, free. Where there are grounds, we write the appeal letter for £9.99. It's a check, not a promise that the penalty goes away.

If you've got two or three years of missed filings stacked up, follow our walkthrough for catching up on overdue dormant company filings. It's the most common situation we help with.

How to stay ahead of the deadline

Three habits make a missed deadline much less likely, for as long as you hold the company:

• Note your ARD and your two deadlines on a calendar that survives phone changes. Google Calendar, iCloud, Outlook — anywhere that gives you a yearly recurring reminder a month before the deadline.
• File two months early. There is zero downside to filing dormant accounts in July when they're due in September. The filing is identical, and you remove the risk of a forgotten password, an out-of-action authentication code, or a Companies House outage on the day.
• Let DormantFile track both deadlines for you. Companies House emails you, but HMRC doesn't — and the CT600 is the one most dormant owners miss.

Filing dormant accounts the easy way

DormantFile is built for exactly this situation: a person who needs to file dormant accounts and a CT600 every year, doesn't want to pay an accountant £200+ for it, and doesn't want to learn accounting software to do it. We track your accounts deadline automatically, file the dormant accounts and the nil CT600 in one flow, and email you reminders well before your accounts are due — and before your confirmation statement, which you file yourself. We also show which directors still have to verify their identity, and check the register daily for changes to the company's directors, address, owners or name. The CT600 works from accounting-period dates you enter yourself — we never guess them — and once a period is added, its deadline joins the same reminders (HMRC's own letter is always definitive). If you'd like to see how it works, take a look at how DormantFile works or check the pricing — most users file both in minutes and pay once per year.