Short answer
The CT600 company tax return is due twelve months after the end of the accounting period. The tax itself is due nine months and one day after the period end. You pay first and file later, and each has its own penalties.
Corporation tax
What is the difference between the CT600 deadline and the payment deadline?
The CT600 is due twelve months after the period end, but the tax is payable nine months and one day after it. Two dates, two penalty regimes, explained.
Written and reviewed by Waqas Sagar Member of ICAEW, Fellow of ACCA, Fellow of AAT, a double graduate and entrepreneur at heart, helping startups grow and serving thousands of businesses nationwide with an excellent team. Published by LimitedCompany.Accountants, 12 London Road, Morden, London SM4 5BQ. Reviewed 12 September 2026 against 2026/27 UK rates and current Companies House and HMRC guidance.
Regulated by
Regulated & AML supervisor
AAT fellow member
Xero Gold PartnerCertified advisor
QuickBooks PartnerCertified ProAdvisor100+ yearsCombined team experienceFully insuredUp to £2m indemnityWhat this means for your company
The CT600 company tax return is due twelve months after the end of the accounting period. The tax itself is due nine months and one day after the period end. You pay first and file later, and each has its own penalties.
01
Three dates on one year end
02
Two penalty regimes
Three dates on one year end
For a 31 March 2027 year end: corporation tax is payable by 1 January 2028, accounts are due at Companies House by 31 December 2027, and the CT600 is due at HMRC by 31 March 2028. Most companies prepare everything once, in time for the earliest date.
Leaving the return to the twelve month deadline means paying a number you estimated nine months earlier, then correcting it. That is how overpayments sit unclaimed and underpayments accrue interest.
Two penalty regimes
A late CT600 costs £100, another £100 at three months, then 10% of unpaid tax at six months and a further 10% at twelve months. Repeated lateness raises the flat penalties to £500 each.
Late payment attracts interest rather than a fixed penalty, but the six and twelve month tax-geared penalties are driven by tax still unpaid, so late payment and late filing compound.
Before you act
Rates, thresholds and deadlines quoted here reflect the 2026/27 UK position and current Companies House and HMRC guidance. Check GOV.UK, or ask us, before relying on them for your own company.
Local help
Talk to a limited company accountant near you
We work with company directors across London and Surrey from our office at 12 London Road, Morden, London SM4 5BQ. Pick your area, or send the form below and we will call you back.
Frequently asked
What is the difference between the CT600 deadline and the payment deadline?: questions directors ask
Can I amend a filed CT600?
Yes, normally within twelve months of the filing deadline.
Do I file a CT600 with no profit?
Yes, if HMRC has issued a notice to deliver. A loss-making company still files, and the loss is recorded for carry forward.
Does the accounts deadline change the tax deadline?
No. They are set independently, which is why three dates exist for one year.
What records are needed for what is the difference between the ct600 deadline and the payment deadline?
Keep bank statements, sales and platform reports, purchase invoices, payroll records, VAT workings, finance agreements and Companies House correspondence. We confirm the exact list at onboarding and identify gaps before a filing deadline becomes urgent.
How much does help with what is the difference between the ct600 deadline and the payment deadline cost?
The fee depends on transaction volume, record quality, VAT and payroll requirements, historic catch-up and the level of reporting needed. We agree a fixed scope and price before technical work starts, with published packages available on our fees page.
Can you take over what is the difference between the ct600 deadline and the payment deadline from another accountant?
Yes. We request professional clearance, collect the prior records and authorities, check the next Companies House and HMRC deadlines, and give you one clear handover list. The process is normally completed remotely.
Can what is the difference between the ct600 deadline and the payment deadline be handled online?
Yes. We work through secure cloud records, scheduled reviews and digital approvals, while keeping a named team available by phone, video call and email. Clients can also visit our Morden office by appointment.
Which accounting software works best for what is the difference between the ct600 deadline and the payment deadline?
We regularly work with Xero, QuickBooks, FreeAgent, Sage and connected sales or expense apps. The right setup depends on transaction volume, integrations and the reports you need, not simply the software brand.
What tax deadlines matter for what is the difference between the ct600 deadline and the payment deadline?
The relevant calendar may include annual accounts, Corporation Tax payment and return dates, confirmation statements, VAT returns, payroll submissions and Self Assessment. We map the dates from your company year end and registrations.
Is this what is the difference between the ct600 deadline and the payment deadline guidance personal tax advice?
No. This page explains general UK rules and common accounting treatment. Your facts, contracts and wider tax position must be reviewed before you rely on a conclusion.
Included approach
Organised, explained, on schedule.
Clear scopeDeadline visibilityHuman support
Check the current rules
Use official information as your reference point.
Deadlines, thresholds and filing rules change. GOV.UK and Companies House publish the current statutory position; advice should then be applied to your company’s circumstances.