What is SEIS? The Complete Guide for Investors (2026)

The Seed Enterprise Investment Scheme — SEIS — is one of the most generous investment tax relief programmes the UK government has ever created. Investors who back early-stage British startups through SEIS can claim income tax relief of 50% on their investment, plus exemption from capital gains tax on any profits. For the right investor, in the right circumstances, it dramatically changes the risk-reward profile of backing early-stage companies.

This guide explains exactly how SEIS works, who qualifies, what the limits are, what the risks are, and how you actually go about making a SEIS investment. It is written for investors, not accountants — in plain English, with the important numbers front and centre.

What is SEIS?

SEIS stands for Seed Enterprise Investment Scheme. It is a UK government programme, administered by HMRC, that provides tax incentives to individuals who invest in early-stage, high-risk companies. The scheme was introduced in 2012 specifically to encourage investment into very early-stage businesses — the kind that have a product idea and perhaps some early customers, but are pre-revenue or very early revenue.

The government offers these tax reliefs because early-stage companies are genuinely risky. Most fail. Without some form of incentive, rational investors would put their money elsewhere. SEIS tips the balance by ensuring that even if a company fails, the investor has already received significant tax relief that partially offsets their loss.

SEIS is the more junior scheme in a pair — the other is EIS (Enterprise Investment Scheme), which covers slightly larger, more mature companies. Many companies raise SEIS first, then follow up with an EIS round once they have more traction.

The five SEIS tax reliefs explained

SEIS offers investors up to five distinct tax advantages. Not every investor will benefit from all five — it depends on your tax position. But understanding all of them helps you see the full value of the scheme.

1. Income tax relief — 50%

This is the headline relief. Invest £10,000 in a qualifying SEIS company and you can reduce your income tax bill by £5,000. The relief is claimed through your Self Assessment tax return and is available in the tax year you make the investment — or you can carry it back to the previous tax year.

The relief is worth 50% of the amount invested, up to a maximum investment of £200,000 per tax year. So the maximum income tax relief in a single year is £100,000. You must have paid (or be due to pay) sufficient income tax to claim the relief — you cannot claim more than your actual income tax liability.

2. Capital gains tax exemption

If you hold your SEIS shares for at least three years and the company succeeds, any profit you make is entirely free of capital gains tax. For a higher-rate taxpayer, CGT on investments outside SEIS would normally be 24%. That exemption can be worth a substantial amount on a successful investment.

3. Loss relief

If the company fails and your shares become worthless, you can claim loss relief. The mechanics are: you first deduct the income tax relief you already received (50%) from the original investment, leaving a net loss. You can then claim relief on that net loss either against income tax (at your marginal rate) or against capital gains.

For a 45% additional-rate taxpayer: invest £10,000, receive £5,000 income tax relief. If the company fails, the net loss is £5,000. Loss relief at 45% is £2,250. Total tax recovered: £7,250 of the original £10,000. The effective maximum loss is £2,750 — or 27.5p in the pound.

4. CGT reinvestment relief

If you have a capital gain from another investment (say, a property sale or a share sale), you can reinvest that gain into SEIS and reduce the CGT bill by 50%. Invest £50,000 of capital gains into SEIS and half that gain — £25,000 — is exempt from CGT. This relief stacks on top of the income tax relief.

5. Inheritance tax relief

SEIS shares held for at least two years qualify for Business Relief, which means they fall outside your estate for inheritance tax purposes. With IHT at 40%, this can be significant for investors concerned about estate planning.

Who can invest in SEIS?

To claim SEIS tax reliefs, you must be a UK taxpayer. Beyond that, the main requirements are:

• You must not be connected to the company — you cannot be an employee, director (in most cases), or hold more than 30% of the shares before investing.
• You must hold the shares for at least three years — selling earlier means you lose the tax reliefs.
• You must be investing your own money — not through a pension or an ISA.
• You must have sufficient income tax or CGT liability to offset against the reliefs.

There is no minimum net worth requirement to invest in SEIS — unlike EIS, SEIS does not require self-certification as a high net worth or sophisticated investor for most routes to market. However, many SEIS opportunities are offered exclusively to high net worth and sophisticated investors, and any financial adviser you work with will assess your suitability.

What companies qualify for SEIS?

Not every startup qualifies. HMRC sets strict rules on the companies that can offer SEIS. The key rules at the time of investment:

• Age: The company must be less than three years old (from its first commercial sale).
• Size: No more than 25 employees and gross assets of no more than £350,000 before the SEIS investment.
• Total SEIS raised: The company cannot have raised more than £250,000 through SEIS in total.
• Trade: The company must carry on a qualifying trade — financial services, property development, and a handful of other sectors are excluded.
• UK-based: The company must be incorporated in and carry on its trade in the UK.
• Not listed: The company cannot be listed on a recognised stock exchange.

Most companies seeking SEIS investment apply to HMRC for Advance Assurance before they start fundraising — this gives investors confidence that the investment will qualify before they commit funds.

SEIS investment limits — 2026

The limits were significantly increased in April 2023 and remain in place for 2026:

• Investor annual limit: £200,000 per tax year (increased from £100,000 in 2023)
• Company lifetime limit: £250,000 total SEIS raised (increased from £150,000 in 2023)

The investor limit applies across all SEIS investments you make in a given tax year. If you invest in multiple SEIS companies, you add up the total — it cannot exceed £200,000. There is no minimum investment amount set by HMRC, though individual companies and platforms will set their own minimums.

The risks of SEIS investing

SEIS investing is genuinely high risk. The tax reliefs are generous precisely because the underlying investments carry a high probability of failure. Before investing, you should understand:

Most early-stage companies fail. Studies consistently show that the majority of seed-stage companies do not return investors' capital. The tax reliefs reduce your effective loss, but they do not eliminate it.

• Illiquidity: SEIS shares are not listed. You cannot sell them easily. Your money is locked up, often for five years or more, until a liquidity event — which may never come.
• Total loss: The company can fail completely. Even with loss relief, you may still lose 27.5p in the pound or more depending on your tax position.
• Tax relief risk: If the company breaks SEIS rules after your investment (by changing its trade, for example), HMRC can withdraw the reliefs and issue a clawback.
• Dilution: Later funding rounds will dilute your shareholding. A 5% stake at SEIS stage can become 1% by the time the company reaches Series B.
• No dividends: Very few early-stage companies pay dividends. Your return depends almost entirely on an eventual exit — a sale, an IPO, or a secondary share sale.

How to make a SEIS investment

There are three main routes to SEIS investment:

1. Direct investment

You invest directly into a specific company. This might be through a crowdfunding platform (Seedrs, Crowdcube), through a syndicate, or through a direct relationship with the founders. You choose the company yourself and do your own due diligence. The minimum investment is usually £500–£5,000 depending on the company and platform.

2. SEIS fund

You invest in a managed fund that pools capital and invests across a portfolio of SEIS-qualifying companies. A fund manager selects the companies on your behalf. This spreads your risk across multiple investments and provides professional deal selection, but you pay a management fee and performance fee.

3. SEIS EIS manager / boutique

Specialist investment managers offer curated SEIS deal flow — typically to high net worth and sophisticated investors — with a higher degree of personal service and due diligence than a platform, but without the full fund structure.

How to claim SEIS tax relief

After you invest, the company sends you a SEIS3 certificate (or your platform provides the equivalent documentation). This confirms that the investment qualifies for SEIS relief. You then claim the relief on your Self Assessment tax return — either in the current tax year or carried back to the previous year.

If you do not normally complete a Self Assessment return, you can claim SEIS relief by contacting HMRC directly. The process is straightforward and HMRC has a dedicated helpline for this purpose.

SEIS vs EIS — which is right for you?

The key difference is the stage of company. SEIS is for very early-stage companies — typically pre-revenue or very early revenue, with fewer than 25 employees and less than three years old. EIS covers slightly larger, more established companies.

SEIS offers higher income tax relief (50% vs 30% for EIS) but lower investment limits (£200,000 vs £1 million for EIS). For investors who want exposure to the earliest stage of company building, SEIS is the right vehicle. For investors who want exposure to companies with a proven business model that are scaling, EIS is more appropriate.

Many investors do both — allocating a portion of their annual tax-advantaged investment budget to SEIS and a portion to EIS.

Summary: is SEIS right for you?

SEIS is appropriate for investors who:

• Have a UK income tax or CGT liability to offset the reliefs against
• Can afford to lock up capital for five or more years
• Understand and accept the risk of total loss
• Want exposure to early-stage British technology, healthcare, or consumer businesses
• Are looking to diversify beyond listed equities, bonds, and property

It is not appropriate as a core or substantial part of a portfolio. It works best as a higher-risk, higher-potential allocation within a well-diversified investment strategy — made by investors who understand what they are buying.

If you are considering SEIS investment, speak to an independent financial adviser who specialises in this area. The tax reliefs are genuinely valuable, but they do not change the fundamental requirement: you need to select good companies and be patient.