Limited Company Tax Deadlines 2026-27

Run a limited company, and you're not dealing with one deadline calendar — you're juggling at least four, run by different parts of government, each with its own rules and its own consequences for getting it wrong. Corporation tax on one timetable. Companies House accounts on another. A confirmation statement with no fine but a much blunter punishment waiting at the end. Your own Self Assessment sitting entirely separately from all of it. None of them line up neatly, and that's exactly why so many directors miss one without ever meaning to.

I keep a running deadline calendar for every single client for precisely this reason — not because directors are careless, but because the system genuinely wasn't designed to be intuitive. This guide sets every deadline out clearly, in one place, for 2026/27, so you know exactly what's coming and when.

Corporation Tax Payment Deadline

Nine Months and One Day After Your Year End

Corporation tax itself is due nine months and one day after the end of your company's accounting period — for a company with a 31 March year end, that means payment by 1 January the following year.

Before Your Tax Return, Not After

Here's the detail that catches out a lot of new directors: the payment deadline comes before the filing deadline for your Company Tax Return, which isn't due for a further three months. You're expected to calculate and pay the tax due before the formal return confirming that figure is actually filed — which is exactly why having your accounts and computations prepared well ahead of the payment deadline matters, rather than leaving everything until the return itself is due.

Quarterly Instalments for Larger Companies

Most small and medium-sized companies pay their entire corporation tax bill as a single payment on this one date. Larger companies — broadly, those with profits above £1.5 million — pay in quarterly instalments instead, under a completely different timetable. For the overwhelming majority of our clients, this simply doesn't apply, but it's worth knowing the rule exists if your company is approaching that scale.

What Happens If You Pay Late

Interest starts accruing automatically from the day after the deadline, calculated daily on the outstanding balance, whether or not your return has been filed yet. It's not a large rate in isolation, but on a significant corporation tax bill left unpaid for months, it adds up — and it's one of the easier costs to avoid entirely with proper planning.

Company Tax Return Deadline

Twelve Months After Your Year End

Your Company Tax Return — the CT600 — is due twelve months after the end of your accounting period, a full three months later than the payment deadline covered above.

The CT600 Itself

The return itself needs to be filed using commercial software rather than a general online portal; HMRC's joint filing arrangement that once let smaller companies file both accounts and the return together through a single simplified route has been phased out, meaning company tax returns and annual accounts are now firmly separate filings, submitted through separate systems.

Penalties for Late Filing

Miss the deadline, and an automatic £100 penalty applies immediately, with a further £100 added if the return is still outstanding three months later. Beyond six months, HMRC can estimate your corporation tax bill itself and add a 10% surcharge on top of that estimate, with a further 10% if it's still outstanding after twelve months — penalties that escalate considerably faster than most directors expect from a first missed deadline.

Companies House Accounts Deadline

Nine Months After Your Year End

Your annual accounts need to be filed with Companies House within nine months of your company's year end for a private limited company — a separate deadline, and a separate filing, from the CT600 covered above, even though they're often prepared from the same underlying set of figures.

Your First Year Is Different

A brand-new company gets a longer window for its very first set of accounts — normally 21 months from the date of incorporation, rather than the standard nine-month rule, which reflects the fact that a company's first accounting period doesn't always line up neatly with a full 12 months of trading.

The Penalty Ladder for Late Accounts

Companies House operates an escalating, automatic penalty ladder for late accounts — starting at £150 for filing up to a month late, rising through £375 and £750 at the three and six-month marks, up to £1,500 for accounts filed more than six months late. Miss the deadline in two consecutive years, and the penalty for the second late filing doubles — a detail that catches out companies who treat one late filing as a one-off, rather than fixing whatever caused it the first time.

Confirmation Statement Deadline

Within 14 Days of Your Review Period Ending

Every company, active or dormant, needs to file a confirmation statement at least once every 12 months, due within 14 days of the end of your review period — which runs from your incorporation date, or from the date of your last confirmation statement, whichever is most recent.

The Fee — Now £50

Companies House fees rose again from 1 February 2026, and the confirmation statement fee is now £50 for online filing, considerably more for paper submissions, which is one more reason online filing is worth defaulting to if you're not already doing so. The fee covers your entire 12-month review period, not each individual filing — if you need to update company details more than once during that period, you don't pay again.

No Fine, But a Blunter Consequence

Unusually among these deadlines, there's no automatic financial penalty for filing a confirmation statement late. That sounds like a relief, and in a narrow sense it is — but the actual consequence is more serious, not less. Persistent failure to file is a criminal offence, and Companies House can move straight to striking the company off the register entirely, which brings its own considerable disruption if the company is still genuinely trading. Recent legislation has also given Companies House new civil penalty powers, so "there's never been a fine for this" is advice increasingly worth treating with caution going forward.

Director Identity Verification Ties In Here Too

Since the identity verification requirements that began in November 2025, your confirmation statement now can't be accepted at all unless each director's personal verification code is included on it — meaning this deadline is now tightly bound up with the identity verification transition covered in our pillar guide. If you haven't verified your identity yet, it's worth sorting out well before your next confirmation statement is due, not in the final few days.

PAYE and National Insurance Deadlines

Monthly Payment Dates

PAYE and National Insurance deducted through payroll are due monthly — by the 22nd of the following month if paying electronically, or the 19th if paying by post, which is one more reason electronic payment tends to be the more forgiving option in practice.

Quarterly Payments for Smaller Employers

If your average monthly PAYE and NI liability is under £1,500, you can arrange to pay quarterly instead of monthly, reducing the administrative burden for genuinely small payrolls — worth asking us about if you're a smaller employer currently paying monthly out of habit rather than necessity.

Penalties for Late or Inaccurate Filing

Late payment penalties escalate based on how many times you've been late within the tax year, and separately, inaccurate Real Time Information submissions can attract their own penalties. Payroll is one of those areas where small, repeated errors tend to compound quietly rather than announce themselves immediately — regular reconciliation catches problems while they're still cheap to fix.

Director's Self Assessment Deadline

31 January — Filing and Payment

Your personal Self Assessment return, covering the tax year ending the previous 5 April, needs to be filed online and any tax due paid by 31 January — the single most well-known deadline in this whole guide, and still the one that catches directors out most often, usually through simple procrastination rather than genuine confusion about the date.

Registering by 5 October

If you're filing for the first time, registration needs to happen considerably earlier — by 5 October following the end of the tax year in which the obligation arose, a deadline that's easy to miss entirely if nobody's told you it exists separately from the filing deadline itself.

Payments on Account

If your tax bill for the year exceeds £1,000 and less than 80% of it was collected at source, HMRC will generally ask for payments on account towards the following year — due alongside your January payment and again the following July — effectively asking you to pay a year and a half of tax in one January sitting, which is exactly the kind of thing worth budgeting for well ahead of the date, not discovering on the day itself.

Every deadline in this guide is entirely avoidable with a bit of forward planning — none of them require genuine complexity to meet, just attention at the right moment. If you'd like us to take that attention off your plate entirely, managing your full compliance calendar across corporation tax, Companies House, payroll and your own personal return, get in touch with the team at Cannon Accountants.

For the wider picture of how these deadlines fit alongside everything else covered in this series, head back to our complete Limited Company Tax Guide 2026/27: Corporation Tax, Dividends & Director Tax →.

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