CT600 Corporation Tax Return Guide UK 2024
Everything you need to know about filing your CT600 Corporation Tax Return with HMRC. Understand the difference between CT600 and annual accounts.
In This Guide
1. What is a CT600?
The CT600 is the Corporation Tax return that all UK limited companies must file with HMRC. It calculates how much corporation tax your company owes based on its taxable profits.
Corporation Tax Rate 2024/25
The main rate is 25% for profits over 250,000 GBP. Small profits rate is 19% for profits under 50,000 GBP. Marginal relief applies for profits between 50,000 and 250,000 GBP.
2. CT600 vs Annual Accounts
Many company directors confuse these two filings. They are different and both required.
| Aspect | Annual Accounts | CT600 |
|---|---|---|
| Filed with | Companies House | HMRC |
| Purpose | Show financial position | Calculate tax owed |
| Deadline | 9 months after year end | 12 months after year end |
| Public record? | Yes - visible to anyone | No - confidential |
| Format | iXBRL (micro-entity can be simpler) | iXBRL with full accounts |
Important
While micro-entities can file simplified accounts with Companies House, they must still submit full accounts with their CT600 to HMRC.
3. Filing Deadlines
| Requirement | Deadline | Example (31 March year end) |
|---|---|---|
| Pay Corporation Tax | 9 months + 1 day | 1 January |
| File CT600 | 12 months | 31 March (next year) |
Pay Before You File
The payment deadline (9 months + 1 day) is BEFORE the filing deadline (12 months). You need to estimate your tax bill and pay on time to avoid interest charges.
4. What to Include in Your CT600
- Full accounts - Balance sheet and profit/loss account
- Tax computations - How you calculated taxable profit
- Supporting schedules - Capital allowances, losses, etc.
5. How to File Your CT600
CT600 must be filed online in iXBRL format. Options include:
HMRC Online Services
Commercial Software
Source: Gov.uk - Company Tax Returns
6. Common Mistakes to Avoid
Confusing filing with payment deadline
Tax payment is due 3 months BEFORE the CT600 filing deadline.
Not including full accounts
Even micro-entities must submit full accounts with CT600.
Forgetting capital allowances
Make sure to claim allowances for equipment and vehicles.