What is SEIS? UK Definition 2026/27
Quick Answer
Seed Enterprise Investment Scheme - 50% income tax relief for investing in start-ups.
Definition of SEIS
The Seed Enterprise Investment Scheme offers 50% income tax relief on investments up to £200,000 per year in qualifying start-up companies. Benefits also include CGT exemption after 3 years, CGT reinvestment relief (50% of gains reinvested are exempt), and loss relief. Its even more generous than EIS but limited to very early-stage companies.
SEIS — Key Facts for 2026/27
| Income tax relief | 50% |
| Annual limit | £200,000 |
| CGT exemption | After 3 years |
| CGT reinvestment relief | 50% exempt |
How SEIS Works — Example
- 1Investment: £100,000
- 2Income tax relief (50%): £50,000
- 3Effective cost: £50,000
- 4If company worth £200,000 after 3 years: No CGT
- 5If fails: Loss relief on £50,000 net cost
How SEIS Affects Your Tax
SEIS offers the most generous tax reliefs of any UK investment scheme, but investments are very high risk. Most start-ups fail. The tax benefits substantially reduce but dont eliminate the risk of total loss.
Official HMRC Guidance on SEIS
For official guidance, refer to HMRC's documentation. Tax rules can change, so always verify current rates and thresholds on gov.uk.
HMRC: SEISFrequently Asked Questions about SEIS
Related Tax Terms
Accuracy Note
This information is for guidance only and is based on 2026/27 tax year rates. Tax rules are complex and your circumstances may differ. For personal advice, consult a qualified accountant or tax adviser.