Corporate Tax Return

Closing Your Business the Right Way

“CT600”? Corporate Tax matters may sound foreign at first. But they are also where thousands are lost or saved and therefore a big chance to strengthen your business. Let us show you how!

CT600 / Corporate Tax return:

The declaration you will learn to love (if you get it right)

The Corporation Tax return (CT600) is required by HMRC to report your company’s taxable profit for a specific accounting period and must be submitted online in iXBRL format together with your statutory accounts. The return includes profit before tax, adjustments for disallowed expenses, capital allowances such as those for equipment or vehicles, R&D tax reliefs where applicable, dividends and directors’ remuneration, Corporation Tax already paid including instalment payments, and the final Corporation Tax liability owed.

But few UK entrepreneurs realise how pivotal CT600 is: Your Corporate Tax return is where your company’s taxable profit is defined, tested, and submitted to HMRC. When preparing a return, necessary adjustments must be made. We highly recommend adjustments to be made by professionals, however, in order to ensure only relevant transactions are factored in i.e., excluding disallowable expenses.

In fact, we often see tax returns that include client entertainment costs which should have been disallowed, fail to apply capital allowances to new equipment, or simply overlook director pension contributions that would have saved thousands. Some returns understate profit due to outdated records; others overstate it by missing key adjustments. Moreover, many are filed late – not due to complexity, but because no one owned the process.

Done correctly, however, the CT600 becomes a point of leverage for you. Applying £10,000 in Annual Investment Allowance could reduce your tax by £2,500. Declaring a £5,000 director pension contribution through the company may cut Corporation Tax while building long-term wealth. Reclassifying a cost from capital to revenue, or adjusting for timing differences, might shift your profit below a tax threshold. These are not “loopholes”, but certainly major opportunities written into tax law. That is, if you know where to look, which is one of our specialties as London chartered accountants for SME.

FAQ

When is my Corporation Tax return due?

You must file your Corporation Tax return (CT600) within 12 months of the end of your accounting period. However, the actual tax payment is due earlier (usually 9 months and 1 day after the year-end).

Are you late for your return? Let us know and we can take care of it to avoid last-minute panic or penalties.

What happens if I file my CT600 late?

HMRC issues automatic penalties:

£100 if you are up to 1 day late
An additional £100 if you are 3 months late
Further penalties of 10% of unpaid tax after 6 and 12 months

Persistent lateness also increases the likelihood of HMRC enquiries such as compliance checks. But our Corporate Tax return services for UK SME ensure that your CT600 is filed accurately and on time. And if you are already late, we can help limit penalties and bring your filings back into good standing.

What information do you need from me to file the CT600?

If we also prepare your accounts, most of the required data would be gathered during that process anyway. Otherwise, we will need:

Your company’s financial year-end date
Profit and loss and balance sheet for the year
Details of salary and dividends
Any asset purchases or disposals
Business bank statements
Any previous Corporation Tax filings or HMRC correspondence

We turn this data into a complete, compliant return, and explain the numbers before submission.

Can you help if my last return was incorrect or missing?

Of course! If you suspect that your last CT600 was incorrect, or if you missed a deadline entirely, we could iron out the issue wherever possible. We will review prior filings, identify errors or omissions, and submit revised returns where necessary. We can also contact HMRC directly to explain and resolve the situation, aiming to reduce penalties – and we have a strong track record when it comes to this. Even if you have not filed for years, we can help you restart with clarity, structure, and no judgment.

How can I reduce my Corporate Tax return legally in the UK?

There are several fully legal and widely accepted ways to reduce your Corporation Tax bill, many of which go unnoticed in self-filed or software-generated returns. For example:

Capital allowances let you deduct the full cost of eligible equipment or machinery. A £12,000 laptop or tools purchase could save up to £3,000 in Corporation Tax under the Annual Investment Allowance (AIA).
Director pension contributions, if paid through the company, are tax-deductible and not subject to National Insurance, meaning a £10,000 contribution could reduce tax by £2,500 while building long-term wealth.
Accrual adjustments for unpaid expenses (e.g. marketing invoices) can lower this year’s profit, even before the payment leaves your bank account.
Correctly timing dividends and salary or using tax-free allowances for business mileage, home office use or training can improve overall tax efficiency.

However, knowing these options exist is not the same as knowing when and how to apply them. Some strategies must be used before year-end; others require supporting documentation or only apply under specific conditions. Misuse can trigger penalties or increase audit risk.

With our Corporate Tax return services for UK SME, we review your full financial position, apply the strategies that suit your business, and ensure every entry in your CT600 is defensible, documented, and as tax efficient as possible.