S/EIS explained: a founder's guide to raising smart

Most founders discover S/EIS the wrong way. An investor mentions it in passing, or a well-meaning advisor drops the acronym into a conversation, and suddenly you’re Googling at midnight trying to understand whether it applies to you and what you’re supposed to do about it.

This guide is the resource I wish more founders had before they started raising. It won’t replace legal advice for startups – and I’ll come back to why that distinction matters – but it will give you the clarity you need to walk into investor conversations as an investable entrepreneur, not a confused one.

What S/EIS actually is

The Seed Enterprise Investment Scheme (SEIS) and the Enterprise Investment Scheme (EIS) are UK government initiatives designed to encourage early-stage investment by offering tax relief to investors who back qualifying startups.

In plain terms: investors who put money into SEIS or EIS-eligible companies can claim back a significant portion of their investment through tax relief. SEIS offers investors up to 50% income tax relief. EIS offers up to 30%. There are also capital gains and loss relief benefits attached to both.

For founders, this matters enormously. It lowers the financial risk for your investors, which makes your opportunity more attractive before you’ve even opened the pitch deck.

Why founders need to understand this – not just investors

There’s a common misconception that S/EIS rules for investors are something investors handle on their own. In reality, the eligibility sits with your company, not the investor. If your business doesn’t qualify, the relief doesn’t exist. And that changes the conversation.

I’ve seen rounds stall because a founder assumed they were eligible and discovered late in due diligence that they weren’t. At that point, an investor who had mentally priced in the tax relief suddenly recalculates the deal. The round doesn’t always survive that recalculation.

Understanding your own eligibility isn’t optional. It’s part of being investor-ready.

SEIS vs EIS: which applies to you?

The two schemes serve different stages.

SEIS is for very early-stage companies. To qualify, your business must have been trading for less than three years, have fewer than 25 employees, and gross assets of no more than £350,000 at the time of the share issue. The maximum you can raise through SEIS is £250,000.

EIS has more headroom. Companies can raise up to £12 million in total EIS funding (with a £5 million annual limit), and the scheme is accessible to businesses with up to 250 employees and gross assets under £15 million. The trading age limit is generally ten years, though rules differ for knowledge-intensive companies.

Most startups begin with SEIS and graduate to EIS as they scale. Some rounds include both simultaneously – investors taking SEIS relief up to the maximum, then EIS relief on the remainder. This is legitimate and worth planning for.

What disqualifies you

This is the part founders often overlook. Not every business qualifies, and the exclusions are specific.

Certain sectors are explicitly ineligible: banking and finance, property development, legal and accountancy services, energy generation in some forms, and farming, among others. If your business model touches any of these, you’ll need professional guidance before making any claims.

The rules around how investment is used matter too. SEIS and EIS funds must be used to grow the business – not to repay existing loans, acquire other companies in the early stages, or purchase assets that aren’t connected to trade. HMRC takes a dim view of schemes that look like tax engineering rather than genuine investment into growth.

A company that has previously raised EIS cannot then raise SEIS. The sequencing is strict. SEIS always comes first.

Advance Assurance – and why you should apply for it

Before you start raising, you can apply to HMRC for Advance Assurance. This is a confirmation that, based on your current structure and plans, your company is likely to qualify for SEIS or EIS investment.

It is not legally binding. HMRC’s final position is always determined at the point of investment. But Advance Assurance gives investors significant comfort. In competitive early rounds, a founder who can show Advance Assurance alongside a strong pitch is in a materially stronger position than one who can’t.

The process is straightforward. You submit a business plan, a description of how you intend to use the funds, and details of your structure. HMRC typically responds within four to six weeks.

If you’re serious about raising, apply before you start outreach. The upside is real, and the downside is a few hours of preparation.

Where legal advice for startups becomes essential

S/EIS is a government scheme, and government schemes come with rules that change. The guidance I’ve outlined reflects the framework as it stands, but the details matter, and the details shift.

More importantly, the interaction between S/EIS eligibility and your company structure – your articles of association, share classes, existing investors, any convertible instruments you’ve already issued – can create complications that aren’t obvious from the headline rules.

This is where proper legal advice for startups isn’t a nice-to-have. A specialist startup solicitor or tax adviser can confirm your eligibility, review your structure, and help you file correctly. The cost of that advice is consistently lower than the cost of a deal falling apart because something was assumed rather than verified.

What this means for your pitch

Understanding S/EIS doesn’t just protect you legally. It actively strengthens your position as an investable entrepreneur.

When you can explain to an investor that your company holds SEIS Advance Assurance, that you’ve planned the sequencing between SEIS and EIS, and that you understand how the relief applies to their specific situation, you signal something that most founders never do: that you’ve thought about this from the investor’s perspective, not just your own.

That shift – from founder asking for money to entrepreneur who understands what it means to receive it – is one of the clearest signals of investor readiness I know.

Capital follows confidence. And confidence, in this case, starts with knowing how the rules work.