CT600 Supplementary Pages Explained: Which Ones Does Your Company Need?
When you file your CT600 company tax return, you may need to include one or more supplementary pages alongside the main form. These additional pages capture specific types of income, reliefs, or circumstances that don't fit on the standard CT600.
Most small limited companies won't need any supplementary pages — the main CT600 covers everything. But if your company has loans to participators, claims R&D relief, or is part of a group, you'll need the right supplementary pages attached.
The CT600 Supplementary Pages at a Glance
| Page | Full Name | When You Need It |
|---|---|---|
| CT600A | Loans to participators | Company has made loans to directors/shareholders |
| CT600B | R&D enhanced expenditure | Claiming R&D tax relief |
| CT600C | Group and consortium relief | Surrendering or claiming group loss relief |
| CT600D | Insurance | Company is an insurance company |
| CT600E | Charities and CASCs | Company is a charity or CASC |
| CT600F | Tonnage tax | Company uses tonnage tax regime |
| CT600G | Corporate Venture Scheme | Company has CVS investments |
| CT600H | Cross-border royalties | Paying royalties to EU companies |
| CT600I | Supplementary charge | Oil and gas companies |
| CT600J | Disclosure of tax avoidance | Using a notifiable tax avoidance scheme |
CT600A: Loans to Participators (Section 455 Tax)
Who needs it: Companies that have made loans or advances to participators (usually directors and shareholders) that are still outstanding at the end of the accounting period.
What triggers CT600A?
If your company has lent money to a director or shareholder — including overdrawn director's loan accounts — and the loan hasn't been repaid within 9 months of the accounting period end, the company must pay Section 455 (s455) tax at 33.75% of the outstanding amount.
Key boxes on CT600A
- A1-A5: Details of each loan or advance
- A10: Total s455 tax due
- A15-A20: Repayments and reliefs claimed
How to avoid s455 tax
The simplest approach: ensure all director's loans are repaid within 9 months of your company year-end. Many directors do this by declaring dividends to offset the loan balance.
Taxpipe handles this: When you enter your director's loan information in the CT600 wizard, we automatically determine whether you need CT600A and calculate any s455 tax due.
CT600B: Research and Development
Who needs it: Companies claiming enhanced R&D expenditure deductions under the SME R&D relief or the merged RDEC scheme (from April 2024).
What qualifies as R&D?
Your project must seek to achieve an advance in science or technology — not just be new to your company. The work must involve overcoming scientific or technological uncertainty.
Common qualifying activities:
- Developing new software algorithms
- Creating new manufacturing processes
- Designing novel engineering solutions
- Developing new formulations or materials
Key boxes on CT600B
- B1: Total R&D enhanced expenditure
- B20: R&D tax credit claimed
- B35: Payable R&D tax credit
R&D rates (2024-25 onwards)
Since April 2024, the merged scheme gives:
- 20% above-the-line credit for most companies
- 27% for R&D-intensive SMEs (R&D spend > 30% of total expenditure)
CT600C: Group and Consortium Relief
Who needs it: Companies that are part of a group and want to surrender or claim losses between group members.
How group relief works
If one company in a group makes a loss and another makes a profit, the profitable company can claim the loss to reduce its corporation tax. Both companies must be in the same 75% group (one holds 75%+ of the other).
Key requirements
- Both companies must have corresponding accounting periods
- A formal claim and surrender must be made
- The surrendering company must consent
CT600D, E, F, G, H, I, J: Specialist Pages
These supplementary pages apply to specific types of companies:
CT600D — Insurance Companies
Only for companies regulated as insurers by the PRA/FCA. Covers the special tax rules for insurance technical provisions.
CT600E — Charities and CASCs
For companies registered as charities or Community Amateur Sports Clubs. Claims exemptions on charitable income and gains.
CT600F — Tonnage Tax
For shipping companies that have elected into the tonnage tax regime — a simplified way of calculating profits based on the tonnage of ships operated.
CT600G — Corporate Venture Scheme
For companies with CVS investments, claiming relief on investments in qualifying small companies.
CT600H — Cross-border Royalties
For companies making royalty payments to associated companies in EU member states, claiming exemption from withholding tax under the EU Interest and Royalties Directive.
CT600I — Supplementary Charge
Specifically for oil and gas companies subject to the supplementary charge on ring-fence profits.
CT600J — Disclosure of Tax Avoidance Schemes
Required when the company has used a notifiable tax avoidance scheme and has a Scheme Reference Number (SRN) from HMRC.
How to Know Which Pages You Need
For most small limited companies, follow this quick checklist:
-
✅ No supplementary pages needed if you:
- Have no outstanding loans to directors/shareholders
- Don't claim R&D relief
- Aren't part of a company group
- Aren't a charity, insurer, or oil company
-
📝 CT600A needed if you:
- Have a director's loan account that's overdrawn
- Made loans to any participator during the period
-
📝 CT600B needed if you:
- Spent money on qualifying R&D
- Want to claim enhanced R&D deductions or credits
-
📝 CT600C needed if you:
- Are part of a group and want to share losses
Filing Supplementary Pages with HMRC
When filing electronically, supplementary pages are included as part of your CT600 XML submission. Your filing software should automatically generate the correct supplementary page data based on your entries.
With Taxpipe: Our CT600 wizard guides you through the relevant questions. If your answers indicate you need a supplementary page, we include it automatically in your HMRC submission — no extra steps required.
Common Questions
Do I need supplementary pages for a nil return?
No. A nil return (zero profit, zero tax) typically doesn't require any supplementary pages unless you have specific circumstances like outstanding director's loans.
Can I file supplementary pages separately?
No. Supplementary pages must be submitted as part of your CT600 return, not as standalone documents.
What if I forget a supplementary page?
You can amend your CT600 within 12 months of the filing deadline. However, late claims for reliefs (like R&D) may be rejected if made outside the time limit.
Do supplementary pages cost extra with Taxpipe?
No. All supplementary pages are included in the standard £59 filing fee. No hidden charges.
Summary
Most small companies only need the main CT600 — no supplementary pages at all. If you do need them, CT600A (director's loans) and CT600B (R&D) are by far the most common.
The key is knowing your company's circumstances. File your CT600 with Taxpipe and our guided wizard will determine exactly which pages you need — automatically.
Need help with your CT600? Start your filing now — just £59, all supplementary pages included.