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File and pay Corporation Tax

Register the company, calculate the liability, prepare the CT600 package, file through recognised software and pay with the correct accounting-period reference.

Step 1

Register and keep records

Make sure HMRC has registered the company and keep the accounts and tax records needed for the return.

Step 2

Choose recognised software

Use HMRC's current list of commercial products that can prepare and submit CT600 returns.

Step 3

Pay HMRC

Use the 17-character reference for the correct accounting period when paying electronically.

Corporation Tax filing checklist

  1. 1. Confirm the accounting period and taxable profit

    Use the dates on the HMRC notice and prepare the tax-adjusted profit, including capital allowances, losses, reliefs and chargeable gains where relevant.

  2. 2. Prepare the complete return package

    The filing normally contains the CT600, required supplementary pages, statutory accounts and detailed tax computations. The accounts and computations use iXBRL format.

  3. 3. File through compatible commercial software

    HMRC's former online filing service closed on 31 March 2026. Use recognised software unless a permitted paper-filing exception applies.

  4. 4. Pay using the correct period reference

    The 17-character payment reference changes each accounting period. Check the notice, reminder or business tax account instead of reusing last year's reference.

Frequently asked questions

Do I need software to file a CT600 Company Tax Return?
Usually, yes. HMRC's own online filing service closed on 31 March 2026. Company Tax Returns, accounts and tax computations are normally filed online using commercial software, with accounts and computations in iXBRL format. Paper filing is restricted to specific exceptions such as a reasonable excuse or filing in Welsh.
What is included in a Company Tax Return?
A Company Tax Return is more than the CT600 form. It normally includes the CT600, any required supplementary pages, the company's accounts and its Corporation Tax computations.
Do I need to register before filing Corporation Tax?
Yes. The company or its agent must register with HMRC before a Company Tax Return can be filed. Registration gives the company a Corporation Tax Unique Taxpayer Reference and access to the relevant HMRC online services.
When do I pay Corporation Tax and file the CT600?
For most companies, Corporation Tax is due 9 months and 1 day after the end of the accounting period, while the Company Tax Return is due 12 months after the accounting period ends. The payment deadline therefore normally comes before the filing deadline. Different payment rules apply to large companies paying quarterly instalments.
How do I pay Corporation Tax online?
Use HMRC's Pay your Corporation Tax bill service and the 17-character payment reference for the accounting period. The reference changes for each period, so copy it from the notice to deliver a return, HMRC reminder or the company's business tax account.
Where can I see my Corporation Tax account?
Sign in to the HMRC business tax account. It can show the company's Corporation Tax statement, accounting periods, payments, liabilities and the payment reference for the period.
Can I amend a Company Tax Return after filing it?
Usually, a Company Tax Return can be amended within 12 months of the filing deadline. If you discover an error, correct it promptly because penalties may apply to inaccurate returns.

Official sources

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