Missing the deadline for filing corporate tax returns can trigger costly penalties from both HM Revenue & Customs (HMRC) and Companies House. Every UK limited company faces unique filing dates based on its own accounting year end—not the tax year—so understanding your deadlines is crucial. The timing for your CT600, Corporation Tax payment, and annual accounts are all different, and mixing them up is a common but expensive mistake. This in-depth guide from Tax Return Accountants explains exactly when each obligation falls due, what happens if you miss a date, and how to avoid the most frequent pitfalls. Whether you’re a small business, landlord, freelancer, or contractor, you’ll find clear answers and practical steps to keep your company compliant and penalty-free in 2025/26 and 2026/27.

Deadline for Filing Corporate Tax Returns

This guide covers all the crucial dates for your company tax return, including the CT600, Corporation Tax payment, and filing accounts with Companies House. By following these steps, you’ll avoid late filing penalties and stay on the right side of HMRC.

Corporate Tax Return Deadlines Explained: CT600, Payment & Accounts

Over 800,000 late filing penalties for Corporation Tax were issued by HMRC in 2024/25 (source: GOV.UK).

Understanding the deadline for filing corporate tax returns is essential for every UK company director. Your CT600 must be filed within 12 months of your company accounting year end. However, the payment of Corporation Tax is due much earlier—9 months and 1 day after the year end. Annual accounts must also be filed with Companies House within 9 months of the same date. Each of these deadlines is distinct, and missing any can result in automatic penalties.

Most business owners wrongly assume all deadlines fall on the same date. In reality, each obligation—CT600, Corporation Tax payment, and Companies House accounts—has its own timescale. For example, if your company’s accounting year ends on 31 March 2026, your Corporation Tax must be paid by 1 January 2027, annual accounts filed by 31 December 2026, and the CT600 return submitted by 31 March 2027.

Every deadline is tied to your specific company accounting year end, not the tax year ending 5 April.

Missing any of these deadlines triggers escalating fines from HMRC and Companies House. The confirmation statement, a separate annual requirement, is due within 14 days of the end of your company’s review period. If you’re unsure of your obligations, a regulated accountant can help you diarise and meet every date.

If you run a company, our Corporation Tax Service ensures you never miss a filing or payment deadline. For official guidance, see GOV.UK: Company Tax Returns.

CT600 filing deadline: what does it mean?

The CT600 is your company’s Corporation Tax return. It must be filed with HMRC within 12 months after your company accounting year end. This form details your company’s taxable profits, reliefs, and tax due for the period.

Corporation Tax payment deadline vs. return filing

Corporation Tax must be paid 9 months and 1 day after your company accounting year end—even if you haven’t yet filed the CT600. This often catches out new business owners who think they can wait until the return is filed before paying.

Accounts filing deadline at Companies House

Your company’s annual accounts must be submitted to Companies House within 9 months of the accounting year end. This is a separate process from the CT600 and is essential for maintaining your company’s good standing.

Corporation Tax Payment Dates: When Is Corporation Tax Due in the UK?

Corporation Tax must be paid 9 months and 1 day after your company’s accounting year end. Do not confuse this with the CT600 filing deadline.

• You must pay Corporation Tax before you file your CT600.
• The payment date is unique to your company’s accounting year end.
• Profits under £50,000 pay the small profits rate (19%); profits over £250,000 pay the main rate (25%).
• Interest and surcharges apply if payment is late.
• Payment is required even if you haven’t yet filed your return.

Here’s how the deadlines play out in practice, depending on your company’s year end:

For small business owners, the payment deadline is critical for cash flow planning. Paying late means not just interest, but also surcharges if you still owe Corporation Tax after 12 months.

Unlike what many guides suggest, you do not have to wait until the CT600 is filed to pay Corporation Tax. In fact, waiting risks unnecessary penalties. Always calculate your likely tax bill in advance and pay on time, even if your accounts are not yet finalised.

For tailored advice, our Limited Company Accountants service helps you plan payments, avoid interest, and stay compliant.

Late Filing Penalties for Corporation Tax: What Happens if You Miss a Deadline?

What are the real costs of missing your company tax deadlines?

Missing the deadline for filing corporate tax returns results in automatic HMRC penalties: £100 if up to 3 months late, £500 for 3-6 months, and £1,000 for 6-12 months. If you’re over 12 months late, HMRC charges an extra 10% of any unpaid tax. Companies House fines for late accounts start at £150 and can rise to £1,500 for delays over 6 months. These penalties can be compounded if you miss deadlines in consecutive years, doubling your costs.

Most business owners are surprised to learn that HMRC and Companies House penalties are entirely separate. Paying one does not cancel the other. For example, a Manchester ecommerce company that missed both deadlines in 2025/26 paid £100 to HMRC and £375 to Companies House—plus additional interest on late Corporation Tax. After switching to Tax Return Accountants, they now use Xero and automated reminders to meet every deadline.

If you believe you have a reasonable excuse, you can appeal HMRC penalties—but success rates are low unless you provide strong evidence (such as hospitalisation or a fire). For Companies House, late penalties are rarely waived and must usually be paid in full.

For more detail, see our Self Assessment Service and GOV.UK: Filing Annual Accounts.

How to File Company Tax Return in the UK: Step-by-Step Process

Imagine a Leicester-based construction company preparing for its year end. The director wants to know exactly how to file the company tax return and avoid mistakes.

• Gather your company accounts, bank statements, and all expense records for the accounting year.
• Log in to the HMRC portal or use approved software such as Xero, QuickBooks, FreeAgent, or Sage Accounting.
• Prepare and submit your CT600 return, ensuring all figures match your final accounts.
• Pay your Corporation Tax to HMRC by the 9 months + 1 day deadline—even if your return isn’t filed yet.
• File your company’s annual accounts with Companies House within 9 months of the year end.
• Save all receipts and confirmation emails for at least 6 years in case of HMRC enquiry.

Using accounting software streamlines the process and reduces the risk of errors. If you’re unsure, our Making Tax Digital Service can help you stay compliant and avoid late filing penalties for corporation tax.

For full guidance, see GOV.UK: Company Tax Returns.

Corporation Tax Return Deadlines for Small Businesses, Landlords, and Freelancers

Over 800,000 late filing penalties for Corporation Tax were issued in 2024/25, affecting businesses of all sizes (source: GOV.UK).

The deadline for filing corporate tax returns applies equally to small businesses, landlords operating via companies, and freelancers who use a company structure. All must file their CT600 within 12 months of their company accounting year end, pay Corporation Tax within 9 months and 1 day, and file annual accounts within 9 months. There are no special concessions for business size or sector.

Landlords with property holding companies and freelancers trading as companies must follow the same process as any other limited company. This includes those in the East Midlands, Manchester, and Nottingham—each has deadlines based on their own company year end, not the 5 April tax year.

• Small businesses: Check your company year end and set reminders for all three main deadlines.
• Landlords: Ensure rental income and expenses are accurately recorded for your CT600.
• Freelancers: Use Xero or FreeAgent to keep records up to date and avoid missing deadlines.
• Contractors: Your IR35 status affects tax calculation, not deadlines.

For landlords, our Landlord Accountants service ensures rent, mortgage, and repairs are reported correctly. If you’re a freelancer, Freelance Accountants can help you stay compliant and avoid costly errors.

Filing Accounts with Companies House: Key Dates and Compliance Tips

Filing accounts with Companies House is a distinct legal obligation, separate from the CT600 and Corporation Tax payment.

Your company’s annual accounts must reach Companies House within 9 months of your company accounting year end. Missing this deadline triggers automatic fines: £150 if up to 1 month late, rising to £1,500 if over 6 months late. Unlike HMRC, Companies House rarely waives penalties—even for a first offence.

Many directors wrongly assume that filing the CT600 with HMRC covers their Companies House obligations. In reality, both filings are required, and both have separate penalty regimes. A Nottingham healthcare company recently faced a £750 Companies House penalty after missing the accounts deadline, despite submitting the CT600 on time.

The confirmation statement is another Companies House requirement. It must be filed within 14 days of the end of your company’s review period. This document confirms your company’s officers, shareholdings, and registered address.

Best practice is to prepare your annual accounts well before the 9-month deadline. Using a Bookkeeping Service helps keep your records up to date and ensures a smooth filing process. For official guidance, see GOV.UK: Annual Accounts.

Your Pre-Submission Checklist: Avoiding Mistakes and Maximising Accuracy

Are you ready to file your company tax return without errors?

• Reconcile all accounts and review every entry for the year.
• Check for missing receipts, invoices, or undeclared income.
• Ensure all deadlines are diarised and responsibilities delegated.
• Consider whether DIY or professional support is right for your business.

Choosing between filing yourself or using a professional accountant is a major decision. The comparison below outlines the key differences:

Professional support not only reduces the risk of late filing penalties for corporation tax, but also identifies tax savings and ensures you never miss a deadline. For transparent fee information, see our Accountant Pricing page or check the ICAEW directory.

Corporation Tax Deadlines for Contractors and Freelancers: What You Need to Know

Imagine a London-based IT contractor operating through a limited company. The deadlines for CT600, Corporation Tax payment, and annual accounts are identical to any other company.

Your IR35 status does not affect the deadline for filing corporate tax returns, but it does impact the tax calculation—particularly for contractors working through their own companies. Using software like Xero, QuickBooks, FreeAgent, or Sage Accounting helps freelancers and contractors meet all deadlines efficiently.

For specialist advice, our Freelance Accountants team supports contractors and freelancers UK-wide.

How to Find an Accountant Near You

Finding a reliable accountant near me can make the difference between missing deadlines and staying fully compliant. Tax Return Accountants offers local accountant support across the UK, including Leicester, London, Birmingham, Manchester, Nottingham, and the East Midlands.

In Leicester, our office at 6 Egginton Street, LE5 5BA, provides in-person and virtual consultations. London clients benefit from our remote service, with all filings handled online for maximum convenience. Birmingham and Manchester businesses can access our chartered accountant near me team for year-round support. Nottingham and East Midlands companies receive tailored advice on corporation tax return for small business and landlord companies alike.

For those searching for a local accountant, always check credentials and client reviews. Our firm is ICAEW regulated, AAT accredited, and rated 4.9/5 on Google Reviews. Contact Tax Return Accountants at 0116 4030595 for a free initial consultation or visit our website for more details.

For official directories, see ICAEW Find a Chartered Accountant or AAT Find an Accountant.

How to Verify an Accountant

5-Step Accountant Selection Process

1. Identify your needs: Are you seeking CT600 filing, bookkeeping, or tax planning?
2. Shortlist 3 accountants: Compare local and online options.
3. Verify regulation: Check ICAEW, ACCA, or AAT credentials.
4. Compare pricing: Request transparent quotes.
5. Book consultation: Meet or call to discuss your requirements.

UK Accountancy Statistics

• Over 93,000 chartered accountants in the UK (ICAEW, ACCA, CIMA, AAT)
• 1.5 million+ businesses enrolled in Making Tax Digital (GOV.UK, 2026)
• 800,000+ HMRC late filing penalties issued in 2024/25 (GOV.UK)
• 62% of UK SMEs use an external accountant (ONS, 2025)

Corporation Tax Deadlines: Industry Examples

Contractors: Must check their company year end and IR35 status. Filing deadlines are the same as all companies.

Freelancers: Use cloud software for real-time tracking and deadline alerts.

Landlords: Ensure all property income and expenses are included in the CT600.

Ecommerce sellers: Reconcile online sales platforms with company bank accounts to avoid HMRC queries.

Construction, Healthcare, Taxi Drivers: Industry-specific expenses need to be correctly categorised for tax relief. Our Bookkeeping Service helps you get this right.

Software Comparison: Xero vs QuickBooks vs FreeAgent vs Sage

Choosing the right software can make filing your company tax return much easier and reduce the risk of errors.

All four major platforms are accepted by HMRC and make it easier to track deadlines and submit returns online.

Online vs Local Accountants: What’s the Difference?

Online accountants offer lower fees and flexible support, while local firms provide personal, face-to-face service. Tax Return Accountants covers both options, with fixed fees from £7.50/month.

Questions Your Accountant Should Ask You

• Are you VAT registered?
• Do you employ staff?
• Do you receive dividends?
• Do you own rental property?
• Do you expect income growth?

When to Change Accountant: 5 Warning Signs

• Slow communication
• Filing errors
• Missed deadlines
• Lack of tax planning
• No Making Tax Digital support

Decision Tree: What Do You Need? → Who to Speak To?

Why Choose Tax Return Accountants?

• ICAEW regulated
• AAT accredited
• Fixed fees from £7.50/month
• Making Tax Digital support
• Dedicated accountant for every client
• UK-wide service, Leicester based
• Free initial consultation

Want to know exactly what you’ll pay? Call 0116 4030595 or email info@taxreturnaccountants.uk for a free, no-obligation quote.

Next Steps

1. Check your company accounting year end and diarise all three key deadlines (CT600, Corporation Tax payment, annual accounts).
2. Decide whether to file yourself or appoint a regulated accountant for support.
3. Contact Tax Return Accountants on 0116 4030595 or info@taxreturnaccountants.uk for a free consultation and deadline review.