The three venture capital schemes trade relief for risk: SEIS gives 50% income tax relief on the youngest companies, EIS 30% on larger unlisted ones and VCTs 20% on a listed fund. The April 2026 changes cut VCT relief and doubled the EIS and VCT company investment limits; SEIS was left alone.
If an SEIS company fails, you can set the loss, after deducting the 50% income tax relief you kept, against your income for that tax year or the one before. On £10,000, that leaves a net loss of £3,000 for a higher-rate taxpayer and £2,750 for an additional-rate taxpayer.
Advance assurance is HMRC's non-statutory, discretionary opinion that a company's planned share issue looks likely to qualify for SEIS or EIS. It does not guarantee any investor's relief, it does not vouch for the business, and it says nothing about whether the company will keep to the rules for the next three years.
SEIS gives UK taxpayers 50% income tax relief on up to £200,000 a tax year invested in new shares of very young companies, with capital gains and loss reliefs on top. The reliefs are generous because the risk is severe: most start-ups fail, and the shares are hard to sell.
Early-stage companies are among the riskiest things a private investor can own: most fail, the shares are hard to sell and any return can take many years. UK tax reliefs soften losses without removing them, and the FCA's crowdfunding rules are built around the risk of losing everything.
Convertible loan notes and advance subscription agreements both let a start-up take money now and issue shares later, usually at a discount to the next round. The difference that matters to UK investors is tax: an ASA can qualify for SEIS or EIS if it meets HMRC's conditions, while shares from a converting loan generally cannot.