For founders chasing their first round of capital, the Seed Enterprise Investment Scheme (SEIS) can feel like a secret handshake in early-stage funding. Those who know, know — and those who don’t often miss out on one of the UK’s most powerful startup incentives.

What is SEIS — and why investors love it

The SEIS was created by HMRC to help the smallest, riskiest UK startups raise capital from private investors.

It allows individuals to claim up to 50% income tax relief on investments of up to £200,000 per tax year, plus Capital Gains Tax (CGT) exemption on profits if they hold the shares for at least three years.

That means an angel investing £20,000 could effectively reduce their tax bill by £10,000 — and if the startup fails, loss relief can offset some of the downside. Hold the shares for two years, and they can also qualify for 100% Inheritance Tax relief (source: Start Up Loans).

For founders, this makes SEIS a magnet for first-time or cautious angels — a way to invest in innovation with a safety net.

How much can you raise under SEIS?

The numbers may sound modest, but they hit hard where it counts.
Eligible startups can raise up to £250,000 through SEIS in total (including any de minimis state aid received in the past three years, as set out by HMRC guidance).

To qualify, the company must:

• Be less than three years old
  
  
• Have under £350,000 in gross assets
  
  
• Employ fewer than 25 full-time equivalent staff
  
  
• Be UK-based, with a genuine trading presence
  
  
• Carry on, or intend to carry on, a new qualifying trade
  
  
• Have no arrangements to become a quoted company and not already trade on a recognised stock exchange
  
  

That early £250k can transform a pre-seed business — enough to make first hires, validate the product, and show traction before scaling or moving to an EIS-eligible round.

Who can’t use SEIS?

SEIS is generous, but it’s not a free-for-all. HMRC excludes sectors that are low-risk, heavily subsidised, or considered unsuitable for venture capital.

Disqualified activities include:

• Banking, insurance, or money lending
  
  
• Property development and leasing
  
  
• Legal, accounting, or financial services
  
  
• Energy generation and farming
  
  
• Dealing in land, shares, or securities
  
  

You also can’t qualify if your company has already received investment via EIS or a Venture Capital Trust (VCT).

The underlying rule is simple: SEIS exists to drive genuine risk-taking innovation, not to prop up predictable businesses. For a full breakdown, see the official list of excluded activities.

Getting Advance Assurance right

One of the smartest moves a founder can make is applying for Advance Assurance — HMRC’s informal thumbs-up that your company and structure are likely to qualify for SEIS. It’s not mandatory, but investors often see it as essential reassurance.

Top tips for approval:

1. Keep it clean. Avoid messy cap tables or complex share classes.
   
   
2. Show investor intent. HMRC likes to see at least one genuine investor lined up.
   
   
3. Prove the risk-to-capital test. Demonstrate that funds are used for growth — not to guarantee returns.
   
   
4. Back it with a solid business plan. Show how funds will drive innovation, not just cover costs.
   
   
5. Get professional advice. A startup lawyer or accountant can prevent costly delays.
   
   

After the fundraise — your compliance checklist

Once you’ve raised your SEIS funds:

• Issue “full-risk ordinary shares” — paid up in cash, non-redeemable, with no guaranteed returns.
  
  
• Submit a Compliance Statement (SEIS1) to HMRC once you’ve traded for four months or spent 70% of the raised funds (official SEIS1 process).
  
  
• Include your business plan, forecasts, accounts, and proof of trade.
  
  
• HMRC will then issue a Letter of Authorisation, a Unique Investment Reference, and SEIS3 certificates for your investors — allowing them to claim their tax reliefs.
  
  

You must stick to SEIS rules for at least three years after the share issue. Break the rules — for example, by changing the trade or structure — and investors could lose their tax relief.

The bottom line

For founders, SEIS isn’t just about compliance — it’s about credibility. It signals that your company is investable, that your investors’ capital is protected within reason, and that you’re playing by the rules of the UK’s venture ecosystem.

Handled well, it’s the kind of insider advantage that can turn a polite “maybe” from an angel into a signed cheque.

Like many good things in finance, SEIS is something you only truly appreciate once you’ve used it — and it can change your trajectory overnight.

Further reading:

• Official HMRC SEIS guidance
  
  
• Advance Assurance application process
  
  
• British Business Bank – guide to SEIS and EIS
  
  
• Start Up Loans – SEIS explained
  
  

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