When Are Dormant Company Accounts Due? Deadlines and Late Filing Penalties (2026)

By DormantFile · Updated 27 May 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 ARD.

The headline numbers: 9 months and 12 months

There are two filings every dormant company 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. Even dormant companies that owe no tax are usually expected to file a nil return unless HMRC has explicitly excused you from doing so.

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 your ARD by:

1. Searching for your company on the Companies House register.
2. Looking at the "Accounts" section — the "Next accounts made up to" date is your current ARD.
3. Checking the "Next accounts due by" date — that is your 9-month deadline.

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 the single busiest month 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, no negotiation, and the penalty applies even if the company has never traded a penny.

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 submitted them. If you post paper accounts and they arrive a day late, that's a late filing.

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: £100 flat penalty.
• 3 months late: another £100, so £200 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 £100 fixed penalties still apply, and they're charged in addition to anything Companies House charges. The fixed penalties also escalate to £500 each if you're late three years 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. The penalties only grow, 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 (AA02) immediately — every day matters because the penalty bands jump at the 1-month, 3-month, and 6-month marks.
3. File any missing CT600s, oldest first. HMRC will accept multiple nil returns at once.
4. Pay any penalty notice you receive — appealing rarely works for "I forgot," but it can succeed for genuine reasons such as bereavement or serious illness.

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 never miss a deadline again

Three habits will protect you for the next decade of holding 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.
• Use a service that tracks 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+ to do it, and doesn't want to fight HMRC's Government Gateway forms. We track both deadlines automatically, file the AA02 and the nil CT600 in one flow, and email you well before each due date. If you'd like to see how it works, take a look at how DormantFile works or check the pricing — most users file in under ten minutes and pay once per year.