Everything You Need to Know About Filing Company Accounts and Corporation Tax

Running a company in the UK comes with its share of legal and financial responsibilities, and one of the most critical among them is filing company accounts and corporation tax. Whether you're a new business owner or a seasoned entrepreneur, understanding the process, deadlines, and requirements involved is essential to stay compliant and avoid penalties.

In this comprehensive guide, we'll walk you through everything you need to know about filing company accounts and corporation tax in the UK.

What Are Company Accounts?

Company accounts, also referred to as statutory accounts, are financial reports prepared at the end of your company’s financial year. These accounts present a clear picture of your business's financial health and are a legal requirement for all limited companies in the UK.

What Do Company Accounts Include?

Typically, your company accounts will contain the following:

Balance Sheet – showing everything your company owns, owes, and is owed at the end of the financial year.
Profit and Loss Account – summarizing your company’s sales, costs, and profits or losses.
Notes to the Accounts – providing detailed information to supplement the financial statements.
Director’s Report – unless exempted as a small company.
Auditor’s Report – for medium and large companies (small companies are usually exempt).

Filing Deadlines for Company Accounts

The deadline for filing your company accounts depends on whether you are a newly incorporated business or an existing one.

New Companies: You must deliver your first accounts within 21 months of incorporation.
Existing Companies: Annual accounts must be filed within 9 months of the end of your financial year.

Late filing results in automatic penalties ranging from £150 to £1,500 depending on how overdue the submission is.

What is Corporation Tax?

Corporation tax is a tax on the profits made by limited companies. Once your company earns a profit, it becomes liable to pay corporation tax, which is currently set at 25% as of 2025 for most companies (though a lower rate may apply to small profit businesses).

You do not receive a bill for this—you must calculate, report, and pay it yourself.

When and How to File Corporation Tax?

Corporation tax is filed through the Company Tax Return (CT600) and submitted to HMRC. The tax return includes:

Company accounts
Calculations of profit and tax
Any other relevant supplementary pages

Filing Deadlines for Corporation Tax

Payment Deadline: 9 months and 1 day after the end of your accounting period
Filing Deadline: 12 months after the end of your accounting period

Note: The accounting period for corporation tax may differ slightly from your financial year.

All submissions must be made online through HMRC’s website using iXBRL (Inline eXtensible Business Reporting Language) format.

Registering for Corporation Tax

You must register for corporation tax with HMRC within three months of starting any business activity, which includes buying, selling, employing staff, advertising, etc.

You’ll need your company’s UTR (Unique Taxpayer Reference), which is usually sent by HMRC shortly after your company is incorporated.

Small Business and Micro-Entity Exemptions

If your company qualifies as a small business or micro-entity, you may be eligible for simplified reporting.

Micro-Entity Criteria

Turnover: not more than £632,000
Balance Sheet Total: not more than £316,000
Employees: no more than 10

Small Company Criteria

Turnover: not more than £10.2 million
Balance Sheet Total: not more than £5.1 million
Employees: no more than 50

If eligible, you can

File abridged accounts
Avoid the requirement of an audit
Submit fewer details to Companies House

Common Mistakes to Avoid

Filing errors can lead to delays, penalties, and potential audits. Here are some common pitfalls to steer clear of:

Missing Deadlines – Penalties for late submissions are automatic and non-negotiable.
Incorrect Figures – Always double-check financial calculations.
Failing to Register for Corporation Tax – Ignorance is not an excuse for HMRC.
Mixing Personal and Business Expenses – Maintain clear and accurate records.
Relying Solely on Software – Accounting software is helpful, but expert review is crucial.

Should You Use an Accountant?

While it's possible to manage your accounts and tax filings on your own, hiring a qualified accountant can save you time, ensure compliance, and potentially uncover tax-saving opportunities.

Accountants are especially useful for:

Complex financial setups
Claiming allowances and reliefs
Ensuring accurate iXBRL submissions
Providing strategic financial advice

Digital Filing Requirements

With the government’s Making Tax Digital (MTD) initiative, businesses are moving towards full digital tax filing. Corporation tax is expected to be included in MTD in the coming years, meaning digital software will be required for submissions.

Now is a good time to adopt accounting software or cloud-based tools that support digital compliance and allow seamless filing with HMRC and Companies House.

Final Thoughts

Filing company accounts and corporation tax can feel overwhelming, but with the right knowledge and systems in place, it becomes manageable. By understanding your responsibilities, sticking to deadlines, and maintaining accurate records, you can ensure your business remains compliant while focusing on growth.

Always remember—penalties and errors can be costly, but they are also entirely avoidable with a bit of planning and professional support.