Calculate income tax relief, CGT reinvestment relief, and loss relief from investing in Seed Enterprise Investment Scheme companies.
This calculator provides estimates for guidance only. SEIS tax reliefs are subject to HMRC rules and conditions including minimum holding periods. Always consult a qualified financial adviser before investing in SEIS-qualifying companies.
The Seed Enterprise Investment Scheme (SEIS) is the UK government's most generous tax relief scheme for investment in early-stage companies. Launched in 2012, SEIS specifically targets seed-stage businesses that are in their earliest phase of development, offering investors even more substantial tax reliefs than the Enterprise Investment Scheme (EIS) to compensate for the higher risk involved in backing brand-new ventures. For the 2026-27 tax year, SEIS provides 50% income tax relief on investments up to GBP 200,000 per year, 50% CGT reinvestment relief on gains used to fund the investment, and loss relief if the company fails. Combined, these reliefs can reduce the effective risk of a total loss to as little as 13.5% of the original investment for an additional rate taxpayer. This calculator helps you understand the full value of SEIS tax reliefs, showing the income tax relief, CGT reinvestment relief, potential loss relief, and the combined effect on your net risk. Whether you are an angel investor, a serial entrepreneur reinvesting gains, or exploring seed-stage investment for the first time, understanding these reliefs is crucial for evaluating the true cost of backing early-stage UK companies.
To calculate your SEIS tax reliefs: 1. Enter your investment amount. The maximum qualifying investment is GBP 200,000 per tax year. You can spread investments across multiple SEIS-qualifying companies within this limit. 2. Select your tax band. This affects the value of loss relief if the company fails and the CGT reinvestment relief calculation, as the CGT rate varies between basic and higher rate taxpayers. 3. Choose whether you are reinvesting a capital gain. If you have a chargeable gain and are reinvesting the proceeds into SEIS shares, 50% of the gain is exempt from CGT. Select yes and enter the gain amount. 4. Select the company fails option to see worst-case loss relief. This models the scenario where the company becomes worthless, showing how much you can recover through loss relief at your marginal income tax rate. 5. Review the results. The calculator shows each relief component, the total reliefs, the effective cost after all reliefs, and the risk reduction percentage. The pie chart visualises the proportion of your investment protected by reliefs.
SEIS reliefs provide the highest level of risk reduction available in any UK tax-advantaged investment scheme: Income Tax Relief: 50% of the qualifying investment, capped at GBP 200,000. For a GBP 100,000 investment, you receive GBP 50,000 income tax relief. This is 20 percentage points more generous than EIS. CGT Reinvestment Relief: 50% of any capital gain reinvested into SEIS is exempt from CGT. For a GBP 30,000 gain reinvested, GBP 15,000 is exempt. At the higher CGT rate of 20%, that saves GBP 3,000 in tax. At basic rate (10%), the saving is GBP 1,500. Loss Relief: If the company fails, the allowable loss is your investment minus income tax relief received. For GBP 100,000 invested with GBP 50,000 relief, the loss is GBP 50,000. At 40% marginal rate, loss relief is GBP 20,000. For a higher rate taxpayer investing GBP 100,000 with a GBP 30,000 gain and company failure: GBP 50,000 income tax relief + GBP 3,000 CGT relief + GBP 20,000 loss relief = GBP 73,000 total reliefs. The net cost of losing everything is just GBP 27,000 -- a 73% risk reduction on the original investment.
SEIS is designed for the very earliest stage companies. To qualify, a company must have been trading for less than 3 years, have fewer than 25 employees, and have gross assets of no more than GBP 350,000. The company must be carrying on or preparing to carry on a new qualifying trade, and it must not be controlled by another company. The maximum amount a company can raise through SEIS is GBP 250,000 in total. This limit applies to the company, not the investor. Many SEIS-qualifying companies are pre-revenue startups seeking their first external funding. The minimum holding period is 3 years. If you sell SEIS shares within 3 years, the income tax relief is clawed back. The CGT reinvestment relief is also clawed back if shares are disposed of within 3 years. Income tax relief can be carried back to the previous tax year, subject to the annual limit for that year. This means an investment made in 2026-27 can be claimed against 2025-26 income tax, which is useful if your tax liability was higher in the previous year. The qualifying trade conditions exclude property development, financial activities, legal and accountancy services, farming, forestry, hotels and guest houses, and several other sectors. Technology companies, manufacturing businesses, and retail companies typically qualify. SEIS and EIS can be combined. Once a company has used its GBP 250,000 SEIS allowance, it may go on to raise further funding through EIS. An investor can hold both SEIS and EIS shares in different companies within the same tax year, using separate annual limits for each scheme. The CGT reinvestment relief is particularly valuable for entrepreneurs who have sold a previous business and are looking to reinvest gains into new ventures. By investing in SEIS-qualifying companies, they can reduce the CGT on their exit while supporting the next generation of UK startups. SEIS compliance certificates (SEIS3 forms) are issued by HMRC after the company has been trading for at least 4 months. Investors should factor in this delay when planning their tax relief claims. All claims must be made through Self Assessment.