SEIS tax relief calculator, 2026/27

How this is calculated

SEIS gives income tax relief of 50.0% of the amount subscribed for qualifying shares, set against the investor's income tax liability for the tax year of investment (or the prior year, if carried back), up to an annual investment cap of £200,000. Anything invested above that cap in a tax year gets no SEIS income tax relief, though it may still qualify for EIS if the company is also EIS-eligible.

Separately, SEIS reinvestment relief lets an investor exempt 50% of a chargeable gain from capital gains tax where the gain is reinvested into SEIS shares in the same or an adjoining tax year, on top of the income tax relief on the same investment, making SEIS one of the few reliefs that can reduce both an income tax bill and a capital gains tax bill from the same subscription.

If the shares are held for at least three years and the company remains qualifying, any eventual gain on disposal is also completely exempt from capital gains tax, and losses net of income tax relief already given can be relieved against income rather than only against gains, which materially changes the real downside risk.

Who and what qualifies

The investing individual must not be connected with the company (broadly, not an employee and not holding more than 30% of the shares), and must subscribe for genuinely new, full-risk ordinary shares rather than shares carrying preferential rights.

The company must generally be under two years old at the date of investment, have gross assets under £350,000 beforehand, fewer than 25 full-time equivalent employees, and must not have raised more than £250,000 in total SEIS investment across its life, alongside carrying on a qualifying trade (most trades qualify, but some, like property investment, do not).

Practical points for investors and companies

Relief is only confirmed once the company has traded for at least four months (or spent 70% of the money raised) and HMRC has issued a compliance certificate, so investors should treat relief as provisional until that certificate (form SEIS3) is received.

Companies planning a SEIS round should apply for advance assurance from HMRC before issuing shares, since this gives investors confidence the structure and trade genuinely qualify before they commit funds.

What is the SEIS income tax relief rate?

SEIS gives income tax relief of 50.0% of the amount invested, up to an annual limit of £200,000 per investor, set against the tax year of investment or carried back one year.

How long do I need to hold SEIS shares?

You need to hold the shares for at least 3 years from the date of issue for the income tax relief to be retained and for any capital gain on disposal to be exempt from capital gains tax.

Can SEIS relief be lost after it is given?

Yes. If you become connected with the company, sell the shares within three years, or the company stops meeting the qualifying trade conditions within three years, HMRC can claw back some or all of the relief already given.

How does SEIS loss relief work?

If the company fails, the allowable loss (cost less any income tax relief already claimed) can be set against income of the same or previous tax year instead of only against capital gains, which can significantly cushion the after-tax downside.