CT600D is the insurance supplementary page of the Company Tax Return. It is a short page with one declaration, about Overseas Life Assurance Business. Very few companies ever need it. This guide explains when you do, how to complete the page in Tax Optimiser, and what each box from D1 to D5 means.
When a company needs a CT600D
File a CT600D, and tick box 110 on the CT600, if the insurance company (including a friendly society) has entered into policies or contracts that have been treated as relating to Overseas Life Assurance Business during the accounting period.
A company that is not an insurer, or an insurer with no Overseas Life Assurance Business in the period, does not file the page.
What the page declares
The page carries no figures. Its one entry, D5, is an X confirming that the company has obtained or completed the certificates, documents, undertakings and declarations required in the Insurance Companies (Overseas Life Assurance Business) (Compliance) Regulations 1995 for the policies and contracts treated as Overseas Life Assurance Business in the return.
Do not complete D5 if they were not created or obtained within the time limits set out in the regulations. The page is then filed with D5 left clear.
Completing the CT600D in Tax Optimiser
Open the period’s Corp Tax Calculations workspace and choose Insurance in the Sections menu. If the period of account is longer than 12 months it is filed as two returns, each with its own CT600D; use the Return 1 and Return 2 buttons to switch between them and answer for each return period.
Step 1 — Say that the page applies
Tick The company has policies or contracts treated as Overseas Life Assurance Business in this period. This is what attaches the CT600D to the return.
Step 2 — Make the declaration, if it applies
Tick the D5 declaration if the certificates, documents, undertakings and declarations were obtained or completed in time. Leave it clear if they were not.
Step 3 — Save and check the return
Click Save. Once the page applies, Tax Optimiser:
- ticks box 110 on the CT600;
- files the CT600D with the return, with the D5 declaration if you made it;
- adds an Insurance page to the computation recording the answers;
- lists the completed form under Supplementary pages on the CT600 Document card, where you can view or download it.
To remove the page, clear the first tick and save.
CT600D box by box
Boxes D1 to D4 — Company information
The company name, tax reference and the period covered by the page. Tax Optimiser copies them from the return; the period cannot exceed 12 months.
Box D5 — Overseas Life Assurance Business
An X if the company has obtained or completed all the certificates, documents, undertakings and declarations required by the Insurance Companies (Overseas Life Assurance Business) (Compliance) Regulations 1995. Leave it blank if they were not created or obtained within the time limits in the regulations.
What Tax Optimiser does not do
The CT600D does not change the tax calculation, and Tax Optimiser does not prepare the specialist computations of a life insurance company. It does not decide whether business is Overseas Life Assurance Business or whether the compliance documents were obtained in time. Those are judgements for the company and its advisers.
Common questions
What is the CT600D?
The CT600D is the supplementary page of the Company Tax Return for insurance companies with Overseas Life Assurance Business. It carries one declaration, in box D5. Box 110 on the CT600 is ticked to show it is attached.
Who has to complete a CT600D?
An insurance company, including a friendly society, that has entered into policies or contracts treated as relating to Overseas Life Assurance Business during the accounting period.
What does box D5 confirm?
That the company has obtained or completed the certificates, documents, undertakings and declarations required in the Insurance Companies (Overseas Life Assurance Business) (Compliance) Regulations 1995.
What if the documents were not obtained in time?
Do not complete box D5. The page is still filed, with D5 left blank.
Does the CT600D change the Corporation Tax payable?
No. The page has no figures and nothing from it is carried to the tax calculation.
Which box on the CT600 shows a CT600D is attached?
Box 110, in the supplementary pages section of the return.
Where to go next
- Corporation Tax in Tax Optimiser — the full journey from trial balance to filed return.
- CT600 box-by-box guide — the supplementary page boxes on the main return.
- HMRC’s CT600D guidance — the official notes for the page.