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What you need to know before submitting your CT600

You must file the CT600 if your company receives a notice to deliver a company tax return from HMRC. Remember, even if your business has suffered losses or you do not need to pay corporate tax, you still need to file.


The deadline for filing is 12 months after the end of the reporting period to which the declaration relates.

Your reporting period usually coincides with the fiscal year covered by your company's financial statements, but it can be different in certain circumstances, such as your first fiscal year. In this case, you must file two tax returns for the first year.

If you are unsure of the end of the reporting period, you can log into your HMRC tax account for confirmation.


The corporate income tax return must indicate:

  • profit or loss of your business for corporate tax (which isn’t the same as profit or loss shown in your annual accounts)
  • your corporation tax bill

You can file your accounts with Companies House and your company tax return with HMRC at the same time if your limited liability company does not need an auditor. You can file these online (you can’t use the paper CT600 form unless you have a reasonable excuse or you want to file in Welsh).

Most small businesses do not need an audit - HMRC states that they usually only need it if the articles of association or shareholders ask for it.


The corporate income tax return is also called CT600. It contains basic business information, but you also need to perform complex calculations. Depending on your business, these are calculations such as:

  • sales income (including profit, trading losses brought forward, property income)
  • chargeable gains
  • profits before deductions and reliefs
  • deductions and reliefs
  • tax reliefs and reductions
  • tax reconciliation
  • losses

The accounting and settlement part of the company's tax return must be in iXBRL (Inline eXtensible Business Reporting Language) format.


Here's what small business owners need to know about filing corporate tax (CT600), but use this information only as a guide and be sure to seek professional advice if you’re unsure of anything. Persona Finance is always ready to help you with CT600!

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