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Filing your Corporation Tax Return (CT600) is a key responsibility for UK businesses. Whether you are starting a new company or running an established one, staying compliant with HMRC is essential to avoid penalties and keep your finances in order. This easy-to-follow guide explains how Corporation Tax filing works, the important deadlines, and how an accountant can make the process simpler.

What is Corporation Tax?

Corporation Tax is a tax on the profits made by companies in the UK. It applies to:

• UK-registered companies
• Foreign companies with a branch or office in the UK
• Some clubs, co-operatives, and associations.
   

Profits from trading, investments, and selling assets (also known as chargeable gains) are all taxable. Even if your business does not make a profit, you might still have to file a Corporation Tax Return.

Who Needs to File a Corporation Tax Return?

If you are a director of a UK limited company , you must file a Corporation Tax Return every year, even if your business made no profit. This includes:

• New and existing limited companies
• Foreign companies operating in the UK
• Some non-profit organisations and societies

⚠️ Common Mistake: Many businesses believe they don’t need to file a return if there’s no profit. This is incorrect—you still need to file unless HMRC tells you otherwise.

Key Corporation Tax Deadlines to Remember 

Missing company tax return deadlines can lead to penalties and interest charges. Keep these important dates in mind:

📍 Example: If your accounting period ends on 31 December, your Corporation Tax must be paid by 1 October of the following year.

How to File Your Corporation Tax Return (CT600)

1. Gather Financial Records
2. Complete the CT600 Form
3. Work Out Your Taxable Profits
4. Submit Your Return Online
5. Pay Your Corporation Tax

🤝 Need help? Doshi Accountants can take care of the whole process of corporation tax return preparation and filing so you don’t have to worry.

Corporation Tax Rates and Allowances (2025)

• 19% on profits up to £50,000
• 25% on profits over £250,000
• Marginal Relief applies for profits between £50,000 and £250,000

Typical Allowable Expenses:

• Staff wages and National Insurance contributions
• Rent, utility bills, and office supplies
• Marketing and website costs
• Software, professional services, and equipment

Claiming these deductions properly can save your business a significant amount in tax.

Common Mistakes to Avoid 

• Missing filing or payment deadlines
• Not registering for Corporation Tax within 3 months of trading
• Making errors in your return
• Assuming you don’t have to file if you didn’t make a profit
• Failing to keep financial records (must be kept for 6 years)

What Happens If You File Late or Make an Error?

• £100 initial penalty
• Higher penalties if more than 3 or 6 months late
• Interest charges on overdue tax
• Potential HMRC  Tax investigations

 
⏳ Tip: It’s best to file your company tax return early.

What’s Changing in 2025?

• Corporation Tax bands remain the same (19% and 25%)
• Making Tax Digital continues to expand
• Check HMRC or your accountant for the latest updates

Why Hire a Corporation Tax Accountant?

• Accurate CT600 preparation and filing
• Full tax relief guidance
• HMRC correspondence handled
• Avoid penalties and overpayments

📞 Call us at 020-8239-4999  📧 Email us at dhruv@doshiaccountants.co.uk for expert help with your Corporation Tax Return Preparation & Filing.

FAQs: Practical Answers to Common Tax Questions

I’m a sole director—do I still need to file Corporation Tax?
Yes—even one-person limited companies must submit a CT600 if the business is active.

What if my company didn’t trade or make profit last year?
You still need to file unless HMRC has declared your company dormant. A zero-profit return is still required in most cases.

When does the countdown for deadlines begin?
From the end of your accounting period, not from company formation. Your accountant can help you align dates properly.

Can I use software to do this myself?
Yes, software like Xero or QuickBooks can help—but without guidance, you may miss allowable deductions or make costly errors.

Can I file early to avoid penalties?
Absolutely. Filing early gives you breathing space and avoids last-minute issues. You can still amend if needed.

Final Thoughts

Contact Doshi Accountants today for help with your Corporation Tax Return. We make it easy, accurate, and worry-free.