SEIS, EIS and UK startup abbreviations explained
You will hear these when you talk to UK angel investors and startup support organisations. This section explains 13 of them in plain English. Jump to the calculators to try them with your own numbers.
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13 terms explained
SEIS
Seed Enterprise Investment Scheme
A UK scheme that gives investors 50% income tax relief for buying new shares in qualifying very young companies.
EIS
Enterprise Investment Scheme
A UK scheme that gives investors 30% income tax relief, and other reliefs, for buying new shares in qualifying companies.
VCT
Venture capital trust
A company listed on the stock market that invests in qualifying smaller companies. Investors who buy new VCT shares can get tax relief.
HMRC
HM Revenue and Customs
The UK tax authority. It runs SEIS, EIS, R&D tax relief and VAT, and gives SEIS and EIS advance assurance.
VAT
Value added tax
The tax a VAT-registered business adds to its sales and pays to HMRC, less the VAT on its own costs. You must register once taxable turnover passes £90,000 in 12 months.
Companies House
The UK registrar of companies. Every UK limited company files its details, accounts and new share issues there, and most of it is public.
SaaS
Software as a service
Software delivered over the internet, usually paid for by subscription.
MVP
Minimum viable product
The simplest version of a product that lets you test your key assumptions with real customers.
PMF
Product-market fit
Evidence that a product meets a real market need: customers keep using it and pay for it.
GTM
Go-to-market
Your plan for launching and selling the product: who buys it, how they hear about it and how you reach them.
TAM
Total addressable market
The total demand for your type of product, if every possible customer bought it.
SAM
Serviceable available market
The part of the TAM you can serve with your business model, product and reach.
SOM
Serviceable obtainable market
The part of the SAM you could realistically win.
Try it with your numbers
SEIS and EIS planner: how much of your round could qualify
Check the headline company limits and see how a round could split between SEIS and EIS. For an investor's own relief, loss relief and gains, use the SEIS and EIS relief calculator.
What could qualify
£500,000
of the £500,000 you want to raise, if the company meets every other rule
- SEIS (50% relief)£250,000
- EIS (30% relief)£250,000
- Neither scheme£0
SEIS company tests
- Passes: Trading for no more than 3 years
- Passes: Gross assets of no more than £350,000
- Passes: Fewer than 25 full-time equivalent employees
- Passes: SEIS raised so far under the £250,000 lifetime limit
EIS company tests
- Passes: Gross assets of no more than £30 million before the issue
- Passes: Fewer than 250 full-time equivalent employees
- Passes: Under the £10 million limit for any 12 months
- Passes: Under the £24 million lifetime limit
- Only the headline limits are checked here. The trade must qualify, the company must be independent, and EIS has an age rule too. Ask HMRC for advance assurance before you pitch.
- Income tax relief in total
- £200,000
- across all your investors
- On a £10,000 SEIS cheque
- £5,000
- net cost £5,000
- On a £10,000 EIS cheque
- £3,000
- net cost £7,000
- Minimum holding
- 3 years
- or relief can be withdrawn
Limits checked on GOV.UK on 21 October 2026: SEIS for companies, EIS for companies and relief for investors.
Try it with your numbers
TAM, SAM and SOM calculator
Size your market from the bottom up: how many customers could buy, what each pays a year, and how much of that you could serve and win.
Your obtainable market
£3.0m
a year, from about 2,500 customers at £1,200 each
- Total addressable (TAM)£240.0m
- Serviceable (SAM)£60.0m
- Obtainable (SOM)£3.0m
- Built bottom-up, from customers times price, which an investor can check line by line. A top-down share of an industry report total is harder to defend.
Last checked . Estimates only, not financial, tax or legal advice: deal terms vary, so check your documents and take advice before you sign. More terms in the startup glossary.