Corporation Tax Deadlines for 2025/26: Key Dates & Penalties for Limited Companies

Introduction

Staying on top of your corporation tax deadlines is essential for avoiding HMRC penalties and keeping your business compliant. Whether you’re running a new limited company or managing a growing business, knowing exactly when to file your Corporation Tax Return (CT600) and pay your tax bill is vital.

In this article, we break down all the key corporation tax filing dates for the 2025/26 financial year, what happens if you miss a deadline, and how to avoid common pitfalls. We’ve also included guidance on dealing with HMRC reminders and how our Corporation Tax Return Services can help

What Is Corporation Tax?

Corporation tax is a tax on the profits of UK limited companies. It must be paid on:

• Trading profits
• Investment income
• Chargeable gains (e.g. selling company assets at a profit)
  

Your business must submit a Corporation Tax Return (CT600) and pay your tax bill annually.

Corporation Tax Deadlines – What Are the Key Dates?

1. Company Tax Return (CT600) Filing Deadline

You must file your Corporation Tax Return within 12 months of the end of your accounting period (also known as your accounting reference date or ARD).

Example:
If your accounting period ends on 31 March 2025, your return must be submitted to HMRC by 31 March 2026.

2. Corporation Tax Payment Deadline

Unlike the CT600 filing, the tax payment is due earlier — within 9 months and 1 day after the end of your accounting period.

Example:
If your year-end is 31 March 2025, your corporation tax payment must be made by 1 January 2026.

Many businesses get caught out because the payment date is before the filing deadline.

Common Mistakes Businesses Make

• Confusing the CT600 filing date with the payment date
• Missing deadlines due to dormant or low-activity company status
• Not notifying HMRC of trading activity or changes
  

If you’ve received a Notice to File from HMRC, you are legally required to submit a CT600 — even if your company made no profit.

What Happens If You Miss the Deadline?

Late Filing Penalties

• 1 day late: £100 penalty
• 3 months late: Another £100
• 6 months late: HMRC estimates your tax bill and charges 10% of the unpaid tax
• 12 months late: Another 10% on top
• 12 months late: Another 10% on top

Repeat offenders face increased penalties. For example, the £100 fine becomes £500 if you’re late three times in a row.

Late Payment Interest

HMRC charges daily interest on late payments — currently 7.75% (as of June 2025), subject to change.

How to Avoid Corporation Tax Penalties

• Track your accounting period and set internal reminders
• Submit early to avoid last-minute issues
• Use cloud accounting to streamline bookkeeping
• Get support from a qualified tax accountant

Corporation Tax for Dormant Companies

Dormant companies must still file a CT600 if HMRC requests it, even with no income. You may be eligible to apply for exemption — we can assist with this.

Need Help with Your Corporation Tax Return?

At Accounting Solutions Manchester, we specialise in preparing and filing Corporation Tax Returns for companies across Greater Manchester. Our team of ACCA-qualified accountants helps businesses:

• Identify allowable expenses and tax reliefs
• Reduce corporation tax liabilities
• Avoid penalties with on-time submissions

We also provide full bookkeeping and year-end accounts services to make things seamless.

How We Can Help?

With over 20 years’ experience supporting limited companies across Manchester and the North West, Accounting Solutions Manchester takes the stress out of meeting your Companies House deadlines. We understand that missing a filing—even by a day—can lead to unnecessary penalties and reputational risk. Our proactive approach helps ensure you stay organised, compliant, and penalty-free.

We offer end-to-end support for all your statutory responsibilities, including:

• Limited company accounts – Preparation and filing of your annual accounts in full compliance with Companies House and HMRC requirements.

• Corporation tax returns – Accurate calculations, early reminders, and on-time submissions to avoid interest charges or late filing fines.

• Tailored support for directors – From personal tax returns to dividend planning, we’ll help you manage your director obligations too.

• VAT returns and advice – From VAT registration to accurate return filing, we ensure you meet Making Tax Digital (MTD) requirements and stay compliant with HMRC deadlines.

• Bookkeeping services – Keep your records up to date with reliable, cloud-based bookkeeping that gives you real-time visibility and helps streamline your year-end accounts.

• Self-assessment tax returns – We handle personal tax returns for directors and shareholders, including dividends, PAYE income, and other earnings.

FAQs About Companies House Filing

What happens if I miss the filing deadline?

HMRC will issue the company with a penalty, which increases the longer you delay. Repeated offences result in doubled penalties.

Can I appeal a late filing penalty?

Yes, but only in exceptional circumstances such as a fire, flood, or illness. Appeals are rarely successful without strong evidence.

Is HMRC filing the same as filing with Companies House?

No. Companies House handles statutory accounts; HMRC requires Corporation Tax returns (CT600) separately.