How SEIS Tax Relief Works

SEIS tax relief is the reward the UK government offers for backing brand new companies. Invest in a qualifying company and you can claim half the money back against your income tax bill, shelter capital gains, and cushion a loss if the company fails. This guide walks through every relief, what it is worth, how to claim it, and the conditions that keep it.

It is written for investors, and it is education rather than advice. The reliefs are generous precisely because early-stage investing is genuinely risky, so read the risk section as carefully as the numbers.

How SEIS tax relief works in one paragraph

You buy new ordinary shares in a company that qualifies for the Seed Enterprise Investment Scheme. Once the company has traded for at least four months and spent at least 70% of the money raised, it asks HMRC to confirm everything is in order and then gives you a certificate called an SEIS3. With that certificate you claim your reliefs through Self Assessment. Hold the shares for at least three years and the reliefs stay yours. That is the whole machine; the rest of this guide is the detail that makes each part work.

If you are still getting your bearings on the scheme itself, start with our plain-English guide to what SEIS is and come back.

Income tax relief: the 50%

The headline relief is simple. Invest £10,000 and you can take £5,000 off your income tax bill for the year. The rate is 50% regardless of whether you pay basic, higher or additional rate tax, and you can invest up to £200,000 in a tax year, which makes the maximum annual relief £100,000.

Three conditions matter more than the rest.

• You need the tax to relieve. The relief reduces your income tax bill; it cannot take the bill below zero. Invest £40,000 with only £15,000 of income tax due and £5,000 of potential relief goes unused.
• The shares must be new ordinary shares. Buying existing shares from another investor earns nothing. The money must go into the company for fresh, full-risk shares.
• You must not be connected to the company. Broadly, holding more than 30% or being an employee blocks the relief, though directors can qualify in defined cases. The glossary covers the connection rules in plain terms.

Carry back: using last year’s tax bill

You can treat some or all of an SEIS investment as if you had made it in the previous tax year, and claim the relief against that year’s bill instead. This matters when your income moves around. A £30,000 investment this year can be split, say £18,000 against this year and £12,000 carried back, wherever the relief works hardest. The carried-back amount still counts against the £200,000 limit of the year it lands in.

Capital gains exemption: the tax-free upside

Hold the shares for at least three years, keep your income tax relief intact, and any gain when you eventually sell is completely free of Capital Gains Tax. There is no cap on that exemption. It is the quiet half of SEIS: the 50% softens the entry, and the CGT exemption means that if you have backed a winner, the upside is yours untaxed.

Reinvestment relief: sheltering an existing gain

If you have made a capital gain elsewhere, selling a property or a business, for instance, and you reinvest that gain into SEIS shares in the same tax year, half of the reinvested gain can be exempt from Capital Gains Tax. With CGT on residential property at 24%, sheltering half of a £100,000 gain is worth £12,000 before the income tax relief is even counted. The exemption sits inside the same £200,000 annual envelope.

Loss relief: the cushion when it goes wrong

Early-stage companies fail often, and SEIS is honest about it. If your shares are sold at a loss or become worthless, you can set the loss, after deducting the income tax relief you already received, against your income or your capital gains. For an additional-rate taxpayer the arithmetic is striking, and we walk it through fully in our guide to how SEIS loss relief works.

A worked example, both directions

Say you are a 45% taxpayer investing £20,000.

Up front: you claim £10,000 of income tax relief, so your real outlay is £10,000.

If the company succeeds and you sell after three years for £60,000, the £40,000 gain carries no CGT. You turned £10,000 of net outlay into £60,000, tax free.

If the company fails and the shares are worthless, your at-risk £10,000 attracts loss relief at your 45% rate, roughly £4,500 back. Total real loss: about £5,500 on a £20,000 investment. That is the shape of the scheme: capped, cushioned downside in exchange for real risk, and an untaxed upside.

Keeping the relief: the three-year rules

Every relief above depends on conditions that run for three years from the share issue.

• Do not sell early. Dispose of the shares within three years and the income tax relief is clawed back.
• Do not become connected. Crossing the 30% line or taking employment can withdraw relief.
• Do not take value out. Loans back to you or unusual benefits from the company reduce relief.
• The company must stay qualifying. If it breaks the scheme rules in the period, investors can lose relief through no fault of their own, which is one reason due diligence matters.

How to claim, briefly

You cannot claim the moment you invest. The company must trade for four months and spend 70% of the raise, then file its compliance statement (form SEIS1) with HMRC. Once HMRC agrees, the company sends you an SEIS3 certificate, and you claim through your Self Assessment return, or through a carry-back claim, using the details on it. The full walkthrough, including PAYE claims and deadlines, is in how to claim SEIS tax relief.

The risk, stated plainly

No relief changes the underlying fact: most very early companies do not succeed, and SEIS shares are illiquid, so you may not be able to sell even if you want to. The reliefs are compensation for risk, not the removal of it. Sensible practice is old-fashioned: invest only money you can afford to lose, spread it across several companies, judge the business before you count the tax, and take professional advice on your own position. Our guide to the risks of SEIS goes deeper.

Does the company actually qualify?

Your reliefs live or die on the company’s status, so the checks are worth a minute: a qualifying trade less than 3 years old, fewer than 25 employees, gross assets under £350,000 before the issue, no more than £250,000 raised under SEIS in total, and a genuine commercial trade that is not on the excluded list. Advance assurance from HMRC is a good sign, not a guarantee. Founders’ obligations are covered in our eligibility guide, and the checklist version makes a quick screen.

SEIS relief next to EIS relief

Investors rarely meet SEIS alone; the same companies graduate to EIS, and many portfolios hold both. The reliefs rhyme but differ where it counts.

The practical difference in the middle row is underrated: SEIS reinvestment relief permanently exempts half the reinvested gain, while EIS deferral parks the gain until the shares are sold. Exemption beats deferral. The full comparison, including VCTs, is in SEIS vs EIS vs VCT.

Direct deals or funds: how people actually invest

There are three common routes into SEIS shares, and the reliefs are identical in each; what changes is who does the work.

• Direct investment: you find the company, judge it, and subscribe. Maximum control, maximum responsibility, and every certificate arrives with your name on it.
• Syndicates and angel networks: a lead investor negotiates and you co-invest. You still hold your own shares and your own SEIS3s, but the sourcing and some diligence are shared.
• SEIS funds: a manager deploys your subscription across a basket of companies. You are still the beneficial owner of each underlying holding, which is why the reliefs flow through, but expect a stack of SEIS3s arriving as the fund deploys, sometimes across two tax years.

None of these routes changes the risk of the underlying companies, and a fund’s diversification is bought with fees and less say. Whichever route you take, the diligence questions in the section below still belong to you.

The diligence that protects your relief

Two kinds of homework matter, and investors habitually do only the first.

Business diligence is the ordinary judgement of team, market, product and runway. The tax relief must never rescue a company you would not otherwise back; a weak company with 50% relief is still a weak company.

Scheme diligence protects the relief itself. Ask for the advance assurance letter and read what was actually assured. Confirm the shares are plain ordinary shares and that your money buys new shares rather than someone’s exit. Check your own position: are you, with your family holdings, anywhere near 30%? Will anything you do for the company look like employment? Five minutes with our eligibility guide, read from the investor’s side, covers the ground, and the common failure patterns show where rounds actually go wrong.

Deadlines, timing, and the paperwork rhythm

Three dates run the whole scheme.

• The share issue date starts the three-year clock for every relief.
• The SEIS3 arrival unlocks the claim. Expect months, not weeks: the company must trade for four months and spend 70% of the raise before HMRC will even look at its compliance statement.
• The claim deadline is five years from the 31 January after the tax year of your investment. Miss it and the relief is simply gone.

Between those dates, keep a simple file per investment: subscription agreement, share certificate, SEIS3, and a note of what you claimed and when. Future you, claiming loss relief or proving a CGT exemption, will be grateful.

Thinking in portfolios, not punts

The arithmetic of early-stage investing is brutal at the level of one company and reasonable at the level of ten. Experienced angels assume several failures, a couple of walking wounded, and hope for one company that pays for the rest. SEIS is built for exactly that shape: the 50% and loss relief keep the failures survivable, and the CGT exemption makes the winner count. What the scheme cannot do is make one concentrated bet sensible, and nothing on this page is a recommendation to make any bet at all.

Where investors lose relief carelessly

• Claiming without the SEIS3, or losing it. No certificate, no claim.
• Selling in year two because an acquirer knocked. The claw-back can be an expensive surprise inside an otherwise happy exit.
• Becoming an employee to help the struggling company you backed. Help as a director, with advice, not as staff.
• The friendly loan back from the company when you are short. Receipt of value rules treat it as getting your investment back.
• Forgetting carry back exists and wasting relief in a low-income year.

A second worked example: sheltering a property gain

Reinvestment relief confuses more readers than any other part of the scheme, so here it is with numbers. You sell a buy-to-let and realise a £60,000 chargeable gain. In the same tax year you subscribe £60,000 for SEIS shares.

• Income tax relief: 50% of £60,000 is £30,000 off your income tax bill, assuming you have that much tax due.
• Reinvestment relief: half the reinvested gain, £30,000, is exempt from CGT. At the 24% residential rate that saves £7,200.
• Combined: £37,200 of tax relief against a £60,000 outlay, before the shares themselves do anything, and any growth on them is CGT-free after three years.

The other half of the gain, £30,000, remains chargeable in the normal way. Reinvestment relief halves the pain; it does not erase it, and the SEIS shares still carry full early-stage risk.

A year in the life of an SEIS investment

Put the whole machine on one timeline and the scheme stops feeling abstract.

• Month 0: you complete diligence, subscribe cash, and the company issues your shares. The three-year clock starts.
• Months 1 to 4: the company trades and spends. Nothing for you to do except keep your subscription papers safe.
• Months 4 to 9, typically: the company files its compliance statement (SEIS1), HMRC authorises it, and your SEIS3 certificate arrives.
• The next Self Assessment cycle: you claim your 50%, choose any carry back, and claim reinvestment relief if you used it.
• Year 3 anniversary: the reliefs become final. From here, a sale is CGT-free and the clawback triggers fall away.

Questions worth asking before you sign anything

• May I see the advance assurance letter, and does the round match what was assured?
• Are these new ordinary shares, with no preferential protections that could void relief?
• How much SEIS capacity does the company have left of its £250,000, counting past raises and any counted grants?
• Who handles the SEIS1, and how quickly have they issued SEIS3s before?
• Am I, with my family holdings, safely below 30%, and is any work I plan to do for the company clearly non-employment?

A company that answers these five crisply is a company that respects your relief. Hesitation on any of them is information too.

What SEIS does not relieve

Three quiet limits round out the picture. Dividends from SEIS companies are taxable in the normal way; the scheme rewards capital, not income. Money advanced as a loan or under a note earns nothing until it becomes a genuine share subscription, which is why instruments matter so much in how rounds go wrong. And the reliefs cannot exceed your own tax: no income tax due means no income tax relief, however qualifying the company. The scheme amplifies a sound tax position; it does not conjure one.

Common questions

How does SEIS tax relief work?

You buy new shares in a qualifying company, receive an SEIS3 certificate once HMRC has confirmed the company met the conditions, and claim 50% of your investment against your income tax through Self Assessment, plus capital gains and loss reliefs.

How much SEIS relief can I get each year?

You can invest up to £200,000 per tax year, giving a maximum £100,000 of income tax relief, and you can carry a claim back to the previous tax year.

Do I pay Capital Gains Tax on SEIS shares?

Not if you hold them at least three years and your income tax relief was given and not withdrawn. Gains on the shares themselves are then CGT-free.

What happens to my relief if the company fails?

Income tax relief already claimed stands, provided you held the shares three years or the company failed genuinely, and loss relief lets you set the remaining loss against income or gains.

Can I claim SEIS relief without an SEIS3?

No. The SEIS3 certificate is the document that supports the claim. No certificate, no relief.