CT600 Supplementary Pages Explained: Which Ones Does Your Company Need?

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

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.

You report the loans and calculate the s455 charge on CT600A. The s455 tax total from CT600A (box A80 on that form) feeds into box 480 on the main CT600. You indicate that you have completed CT600A by ticking box 95 on the main form.

How s455 tax works

S455 tax is a temporary charge: once the director repays the loan, the company can claim a refund under CTA 2010 s.458. Be aware of the "bed and breakfast" rule — if a loan of £5,000 or more is repaid but a similar amount is re-borrowed within 30 days, the repayment is disregarded for s455 relief purposes.

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.

If your company has outstanding loans to participators, you will need specialist tax software or a tax adviser to complete CT600A correctly.

CT600B: Controlled Foreign Companies and Hybrid Mismatches

Who needs it: Companies that:

• Control a foreign company (a "Controlled Foreign Company" or CFC) — broadly, a non-UK resident company in which a UK company holds a significant interest and exercises control
• Have a permanent establishment abroad (such as a branch office in another country) and are claiming an exemption
• Have hybrid and other mismatch arrangements — cross-border structures that exploit differences between the tax rules of two countries to achieve a double deduction or a deduction without a corresponding income inclusion

For most small UK companies that operate only within the UK and don't own or control overseas businesses, CT600B will not be needed.

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 and the Remaining 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. Note: this is NOT for companies that merely donate to charities — charitable donations are entered in box 305 on the main form.

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 — Northern Ireland

For companies with profits subject to Northern Ireland corporation tax provisions. There is no separate NI Corporation Tax rate currently in force, so this page is rarely used in practice.

CT600H — Cross-border Royalties

For companies making royalty payments to companies in other countries — for example, patent fees, trademark licences, copyright payments, or software licensing fees paid to foreign companies.

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. This is not about ordinary tax planning — it applies only to specific HMRC-flagged marketed schemes.

CT600K — Restitution Tax

For companies that received restitution interest — compensation interest paid by HMRC for previously overpaid tax. This interest is subject to a separate 45% restitution tax charge.

CT600L — Research and Development

For companies claiming R&D tax relief. If your company spent money solving scientific or technological uncertainties — developing new software, processes, materials, or engineering solutions — the R&D claim goes here. You tick box 142 on the main CT600 to indicate you are completing CT600L.

R&D rates from April 2024 under the merged scheme:

• 20% above-the-line credit for most companies
• 27% for R&D-intensive SMEs (R&D spend exceeds 30% of total expenditure)

CT600M — Freeports and Investment Zones

For companies operating in a designated Freeport or Investment Zone tax site and claiming enhanced capital allowances or other reliefs.

CT600N — Residential Property Developer Tax (RPDT)

For residential property developers with annual profits over £25 million subject to RPDT.

CT600P — Creative Industries

For companies claiming creative industry tax relief — film, TV, video games, theatre, orchestra, museums and galleries exhibition tax relief.

How to Know Which Pages You Need

For most small limited companies, follow this quick checklist:

1. ✅ 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

2. 📝 CT600A needed if you:

   • Have a director's loan account that's overdrawn
   • Have loans to a participator that remain outstanding at the 9-month point after the accounting period end

3. 📝 CT600C needed if you:

   • Are part of a group and want to share losses

4. 📝 CT600E needed if you:

   • Are a registered charity or CASC

5. 📝 CT600L needed if you:

   • Spent money on qualifying R&D work

Filing Supplementary Pages with HMRC

When filing electronically, supplementary pages are included as part of your CT600 XML submission. Your filing software should generate the correct supplementary page data based on your entries.

With Taxpipe: Our CT600 wizard covers the main form and CT600E (charities and CASCs). For simple trading companies, property landlords, and charities/CASCs, file your CT600 with Taxpipe — just £59. If your company needs other supplementary pages such as CT600A or CT600L, you will need specialist tax software or an accountant.

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.

Which supplementary pages does filing software typically support?

This varies by software. Check your software's documentation before filing — if your company needs a supplementary page that your software doesn't support, you may need specialist tax software or a tax adviser.

Summary

Most small companies only need the main CT600 — no supplementary pages at all. If you do need them, CT600A (director's loans) and CT600L (R&D relief) are by far the most common.

The key is knowing your company's circumstances. If you're a simple trading company, property landlord, or charity/CASC, start your CT600 filing with Taxpipe — just £59.

Need help with your CT600? Start your filing now — just £59.

Related Articles

• R&D Tax Relief for SMEs: How to Claim on Your CT600
• Corporation Tax on Bank Interest: How It Works
• Corporation Tax on Overseas Income: Guide for UK Companies