Company deadline guide
Corporation Tax payment and CT600 deadlines explained with examples, first year rules, quarterly instalments, weekends and separate Companies House dates.
Short answer
Most limited companies pay Corporation Tax nine months and one day after their accounting period ends and file the CT600 within 12 months. Large companies can pay by quarterly instalments, and first accounts may cover two tax periods.
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.
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QuickBooks PartnerCertified ProAdvisor100+ yearsCombined team experienceFully insuredUp to £2m indemnityThe Corporation Tax payment deadline comes before the company tax return deadline. Directors often confuse it with the Companies House accounts date, but each obligation has its own timetable and consequences.
Payment is normally due after nine months and one day
The CT600 is normally due after 12 months
Accounts usually reach Companies House after nine months
First years can create two CT600s
For a 12 month accounting period ending 31 March 2027, a small company normally pays Corporation Tax by 1 January 2028. The CT600 is due by 31 March 2028. Statutory accounts normally go to Companies House by 31 December 2027.
Calculate the tax before the payment date, even though filing can happen later. Preparing everything for the earliest deadline avoids paying an estimate and correcting it months afterwards.
A company's first Companies House accounts can cover more than 12 months, but a Corporation Tax accounting period cannot. A 13 month first set of accounts therefore usually creates one 12 month CT600 and a second one month CT600, each with its own payment date.
Do not copy the Companies House period into one tax return. Accounting software and the HMRC notice to deliver should show the split periods.
Companies with augmented profits above the large company threshold can pay Corporation Tax in instalments before the period ends. The usual £1.5 million threshold is divided by associated companies, and very large companies have an accelerated regime.
There are exceptions and first-year rules, so a growing group should forecast the threshold before relying on the normal nine month deadline.
HMRC must receive cleared funds by the due date. If it falls on a weekend or bank holiday, choose a payment method that reaches HMRC by the last working day before it, unless the current HMRC payment guidance says otherwise for that method.
Interest runs from the day after the due date until payment. Contact HMRC early where cash flow prevents full payment and propose an affordable Time to Pay arrangement.
Put the accounting reference date, Companies House accounts date, Corporation Tax payment date and CT600 filing date in one calendar. Add VAT, payroll, confirmation statement and Self Assessment dates where relevant.
Our free deadline calculator turns the company year end into the main filing dates. Rates and deadlines are reviewed for 2026/27, but HMRC interest rates and individual circumstances can change the result. Check the linked official guidance or ask us before acting.
Primary references
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Frequently asked
Normally nine months and one day after the end of the accounting period for a small company.
Normally 12 months after the end of the Corporation Tax accounting period.
The legislation sets different deadlines. The payment deadline is usually about three months earlier than the CT600 deadline.
It can. If the first accounts cover more than 12 months, the company normally files two CT600s because a tax accounting period cannot exceed 12 months.
No. Quarterly instalments generally apply to larger companies, with thresholds reduced for associated companies.
Contact HMRC promptly about Time to Pay. Late payment interest still runs, but an agreement can prevent escalation.
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.
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.
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.
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.
Included approach
Check the current rules
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.
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