SEIS Tax Relief Calculator 2025/26

What Is the Seed Enterprise Investment Scheme (SEIS)?

The Seed Enterprise Investment Scheme (SEIS) is a UK government programme designed to stimulate investment into the earliest, most high-risk stage of a company's life — the seed stage. Introduced in April 2012, SEIS is widely considered one of the most generous tax-advantaged investment schemes in the world. For every £1 an eligible investor puts into a qualifying SEIS company, the government effectively subsidises 50p through income tax relief, dramatically reducing the financial downside of backing unproven startups.

In the 2025/26 tax year, individual investors can invest up to £200,000 in SEIS-qualifying companies (this limit was doubled from £100,000 by the Finance (No. 2) Act 2023). The income tax relief is 50% of the amount invested, meaning a maximum tax reduction of £100,000 in a single year. Crucially, the relief is non-refundable — you can only claim up to the amount of income tax you actually owe for that year. Unused relief cannot ordinarily be carried forward, though you can carry it back to the prior tax year if you did not use your full annual limit then.

Company Eligibility Requirements

Not every startup qualifies for SEIS. HMRC imposes strict conditions on the companies that can raise SEIS funding. At the time of the SEIS share issue, the company must meet ALL of the following criteria:

• Age: The company must have been carrying on a qualifying trade for fewer than 3 years (extended to 10 years for knowledge-intensive companies under EIS, but SEIS retains the 3-year limit).
• Size: Fewer than 25 full-time equivalent employees at the time of the share issue.
• Assets: Gross assets must not exceed £350,000 before the share issue.
• Location: The company must be UK-incorporated and have a permanent establishment in the UK.
• Trade: The company must carry on a qualifying trade — excluded activities include property development, financial services, legal or accountancy services, farming, and certain energy generation activities.
• Previous funding: The company must not have received EIS investment or a Venture Capital Trust (VCT) investment prior to raising SEIS funding. However, it can subsequently raise EIS after SEIS.
• Lifetime SEIS cap: The company can raise a maximum of £250,000 under SEIS in total.

Investor Eligibility for SEIS

To claim SEIS income tax relief, you must be a UK taxpayer with a sufficient income tax liability to offset against the relief. SEIS relief is not available to investors who are:

• Employees of the company (though directors may qualify under certain conditions)
• Partners of an employee or director in a way that creates a connection
• Holders of more than 30% of the ordinary share capital, voting rights, or loan rights in the company

There is no minimum investment amount for SEIS. However, from a practical standpoint, many SEIS investment platforms and syndicates have minimum ticket sizes of £1,000 to £5,000. The maximum is £200,000 per tax year per individual investor.

How to Claim SEIS Relief on Your Tax Return

Claiming SEIS income tax relief requires the following steps:

1. Obtain the SEIS3 certificate from the company. This is the official HMRC form that confirms the shares qualify for SEIS relief. The company can only issue SEIS3 certificates after HMRC has confirmed the shares are qualifying — this process typically takes 3–6 months after the investment date.
2. Complete your Self Assessment tax return. Report the SEIS investment on the supplementary SA300 (or SA101) pages under "Other tax reliefs." Enter the amount invested and the SEIS3 reference number.
3. HMRC adjusts your tax liability. The 50% income tax relief is applied directly to reduce your income tax due for that year. If you have overpaid, you will receive a repayment.
4. Consider carry-back. If you invest in SEIS shares between 6 April and 31 January of the following tax year, you can elect to treat the investment as if made in the prior tax year — particularly useful if you had a higher income in the previous year.

CGT Reinvestment Relief Under SEIS

One of the lesser-known but highly valuable SEIS benefits is CGT reinvestment relief. If you have realised a capital gain from another asset (for example, selling shares, a buy-to-let property, or a business) and you reinvest the proceeds into SEIS-qualifying shares in the same tax year, 50% of that capital gain is exempt from CGT. This relief is separate from the income tax relief and can be claimed on top of it.

For example: You sell shares and realise a £50,000 capital gain. You invest £50,000 into SEIS. You can exempt £25,000 of that gain from CGT (50%). At the standard CGT rate of 20% for higher-rate taxpayers, this saves £5,000 in CGT. Combined with £25,000 income tax relief (50% × £50,000), your total tax saving on a £50,000 SEIS investment could be £30,000 — a 60% effective subsidy from HMRC.

Loss Relief: Protecting Against Failure

The unfortunate reality of seed-stage investing is that many companies fail. SEIS loss relief provides a safety net: if a company in which you hold SEIS shares becomes worthless (formally dissolved or shares become negligible in value), you can claim loss relief. The loss is calculated as the net investment after income tax relief has been applied, and this net loss can be set against your income tax in the year of the loss or the prior year.

Worked example: You invest £20,000 in SEIS. You receive £10,000 income tax relief, making your net cost £10,000. The company fails and the shares are worthless. The £10,000 net loss can be set against income. As a 45% additional-rate taxpayer, you reclaim £4,500. Your effective total loss on a £20,000 investment is just £5,500 — HMRC has shared 72.5% of your risk.

SEIS vs EIS vs VCT: Comparison

SEIS, EIS, and VCT are the three main tax-advantaged investment schemes in the UK. They target different stages of company development and offer different risk-reward profiles:

HMRC Advance Assurance and the SEIS3 Certificate

Companies seeking SEIS funding will often apply for HMRC Advance Assurance before they issue shares. This is not legally required, but it gives investors comfort that HMRC considers the company and proposed share issue to be likely to qualify for SEIS relief. Advance Assurance is not a guarantee — HMRC can still refuse relief if circumstances change or the application contained errors.

After shares have been issued, the company applies to HMRC for a compliance statement. Once HMRC is satisfied, it issues SEIS3 certificates to the company, which then distributes them to investors. Only upon receipt of the SEIS3 can you formally claim relief on your tax return. Investors should request confirmation of HMRC Advance Assurance status before committing funds.