| Overview |
Supplementary schedules are additional CT600 pages that are included in a Corporation Tax return where specific circumstances apply — for example, R&D claims, group relief, or charitable donations. This article explains how to add supplementary schedules and what each one covers.
| How to Add a Supplementary Schedule |
- Open the CT return and expand the CT navigation toolbar using the toggle switch at the top left.
- Click the Template tab.
- Click the Supplementary Schedules button.
- A list of available schedules appears. Tick the checkbox next to each schedule you want to include.
- The selected schedules will appear in the Table of Contents on the left and can be accessed from there.
| ✔ Tip: Supplementary schedules only appear in the Table of Contents after they have been ticked in the Supplementary Schedules screen. If a schedule is missing from the table of contents, check that it has been ticked here. |
| Supplementary Schedules — Express Template |
| Schedule | Name | When to Include |
|---|---|---|
| CT600A | Loans to Participators | Where the company has made loans to directors or participators |
| CT600C | Group and Consortium Relief | Where the company is claiming or surrendering group relief |
| CT600D | Insurance | For insurance companies only |
| CT600E | Charities and Community Amateur Sports Clubs | For charitable companies or CASCs |
| CT600J | Disclosure of Tax Avoidance Schemes | Where a DOTAS disclosure number is required |
| CT600K | Restitution Tax | Where restitution interest has been received |
| CT600L | Research and Development | Where the company is making an R&D claim under any scheme |
| Marginal Relief | Marginal Relief calculation | Where the company's profits fall between £50,000 and £250,000 |
| Capital Allowances | Capital Allowances schedule | For plant and machinery and other qualifying capital expenditure |
| Property | Property Income | Where the company has UK property income |
| Capital Gains | Chargeable Gains | Where the company has disposed of a chargeable asset |
| Research and Development | R&D detail page | For R&D relief calculations — see also CT600L |
| CT600E — Box 195: 2026 Update |
From CT 2026, CT600E now supports up to 12 entries for Box 195. BrightTax automatically applies the expanded entry limit for accounting periods covered by the CT 2026 form — no action is required on your part.
| Marginal Relief — Important Note |
If the Marginal Relief schedule is not included in the return, Box 329 on the CT600 will not be automatically ticked. This will cause an error where the CT rate shows as 25% instead of the expected blended rate for profits between £50,000 and £250,000.
| ⚠ Important: Always include the Marginal Relief schedule for companies with profits between £50,000 and £250,000. If the tax rate is showing at 25% when it should be lower, check whether Marginal Relief has been ticked under Supplementary Schedules. |
| CT Options |
CT Options is also accessible from the Template tab. Use this to state whether you have a reason for not including accounts with a submission — this bypasses the system validation that requires an iXBRL file to be attached before submission.
| Frequently Asked Questions |
Q: Can I add a supplementary schedule after I have already started entering data?
A: Yes. Supplementary schedules can be added at any point before submission. Tick the required schedule under the Template tab and it will appear in the Table of Contents.
Q: Can I remove a supplementary schedule I no longer need?
A: Yes. Return to the Template tab > Supplementary Schedules and untick the schedule. Any data entered on that schedule will be removed.
Q: The CT600L schedule does not seem to be calculating the R&D PAYE cap correctly — why?
A: From CT 2026, the R&D PAYE cap is time-apportioned for accounting periods that are not exactly 12 months. BrightTax calculates this automatically. If the figure still appears incorrect, check the accounting period length on the return.
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