The rates
| Profit band | Rate |
|---|---|
| £0 - £50,000 | 19% (small profits) |
| £50,001 - £250,000 | 26.5% effective (marginal relief) |
| £250,000+ | 25% (main rate) |
Associated companies rules
The £50K and £250K thresholds are divided by the number of associated companies. If you and a connected person (typically a spouse or family member) each own a Ltd company, the thresholds for each company are halved (£25K small profits, £125K main rate).
This catches a lot of family-run group structures. A specialist accountant will check your associated company position before any tax planning advice.
Payment and filing deadlines
- Corporation Tax payment: 9 months and 1 day after the end of the company's accounting period.
- CT600 return filing: 12 months after the end of the accounting period.
- Statutory accounts to Companies House: 9 months after year-end (private Ltd) or 6 months (public Ltd).
- Confirmation Statement: annually, on the anniversary of incorporation (plus a 14-day grace period).
Common reliefs
- Annual Investment Allowance (AIA) - 100% deduction on qualifying capital expenditure, up to £1M/year.
- R&D tax credits - for genuine technological/scientific advancement (not just any software work).
- Patent Box - 10% effective CT rate on profits from patents.
- Loss carry-back/forward - trading losses can offset prior or future profits.
- Group relief - losses can be transferred between group companies.
Frequently asked questions
When is my first Corporation Tax payment due?+
9 months and 1 day after the end of your company's first accounting period. For a Ltd incorporated on 1 March 2025, the first year-end is typically 31 March 2026, and CT is due 1 January 2027.
What's marginal relief?+
Marginal relief is the formula that bridges the 19% small profits rate and the 25% main rate, producing a 26.5% effective rate on profits between £50K and £250K. It's not a separate filing - just the way HMRC calculates CT in this band.
Tell us about your situation. We'll match you with the right specialist.
No fees, no obligation. We come back within 1 working day.