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by Undo Capital
December 15, 2025
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What Is SEIS (Seed Enterprise Investment Scheme)?

SEIS/EIS advance assurance is a non-binding written opinion from HMRC confirming that a planned share issue should qualify for the Seed Enterprise Investment Scheme (SEIS) or Enterprise Investment Scheme (EIS), giving investors early comfort on future tax relief.

SEIS (Seed Enterprise Investment Scheme) Meaning

SEIS stands for Seed Enterprise Investment Scheme, a UK programme that de-risks very early-stage investing through income and capital gains tax reliefs. When founders and investors ask “What is SEIS?” or search for the SEIS definition, they want to understand whether a startup qualifies and how much relief is available.

The meaning of SEIS, and SEIS meaning in practice, becomes crucial at the advance assurance stage, when HMRC effectively confirms that the planned share issue should meet the rules.

To find out more about SEIS and EIS, go to Undo Capital guide.

Disclosure Notice: This communication is issued by Undo Capital Limited (“Undo Capital”) and is provided strictly for informational purposes only. It contains general information and should not be relied upon as accounting, business, financial, investment, legal, tax, or other professional advice. Undo Capital is not regulated by the Financial Conduct Authority (FCA) and does not provide investment, financial, or tax advice. Our services are designed to assist startups and businesses with company formation, legal agreements, and funding-related documentation. Nothing in this communication constitutes, or should be construed as, a recommendation, offer, or solicitation to purchase or sell any security or financial instrument.
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Undo Capital handles everything — SEIS/EIS, investor agreements, share issue, and filings — in one simple, automated platform.

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Disclaimer: Our services are designed to assist startups and businesses with company formation, legal agreements, and funding-related documentation. We do not provide investment advice, financial advice, or tax advice, nor are we regulated by the Financial Conduct Authority (FCA). Participating in startups and early-stage enterprises carries inherent risks, including limited liquidity, absence of dividends, potential loss of investment, and dilution. Any decisions regarding investments should be made independently by the investor as part of a well-diversified portfolio.