SEIS income tax relief: how the 50% works in practice

In short: SEIS income tax relief reduces your income tax bill by 50% of what you invest, on up to £200,000 of investment in a tax year, giving a maximum reduction of £100,000. The mechanics are set out in HMRC helpsheet HS393.

It reduces tax, not income

This distinction matters. SEIS relief is not a deduction from taxable income like a pension contribution. It is a reduction in the tax you owe. So the relief is worth the same to a basic-rate taxpayer as to an additional-rate taxpayer, provided both have enough liability to absorb it.

The £200,000 ceiling

The annual limit applies to the investor, across all SEIS investments in the tax year, not to each company. It rose from £100,000 to £200,000 for shares issued on or after 6 April 2023. Investing more than £200,000 in a year is possible, but the excess attracts no SEIS relief.

Where more than one investment is made in the year and the total exceeds the cap, relief is applied to the shares in the order they were issued until the cap is reached.

When your liability is smaller than the relief

Relief can reduce a liability to nil, but no further. There is no repayment of the shortfall and no carry forward to a future year. The one route available is carry back, which treats the investment as if it had been made in the previous tax year and applies the relief against that year's liability instead.

When you can claim

You cannot claim at the point of investment. The company must first have carried on its qualifying trade for four months, or spent at least 70% of the money raised. It then submits a compliance statement to HMRC, and once HMRC authorises it, the company issues you an SEIS3 certificate. The claim follows that. The full sequence is in advance assurance and the SEIS3 certificate, and the claim itself in how to claim SEIS relief.

There is a long stop: a claim must be made within five years of 31 January following the tax year in which the shares were issued.

Relief can be taken back

If you sell the shares within three years, become connected with the company, receive value from it, or the company stops qualifying, HMRC can withdraw or reduce the relief and assess the tax. The three-year holding period guide sets out the triggers.