Seed Enterprise Investment Scheme (SEIS)

Q: What happens if I miss the Self Assessment deadline?

The Self Assessment deadline is 31 January (online filing) for the previous tax year. Miss it and HMRC apply an automatic £100 penalty. Beyond that: £10 per day from 3 months late (capped at £900), 5% of tax due at 6 months late, and another 5% at 12 months late, under Schedule 55 of the Taxes Management Act 1970. If you have a genuine reason (serious illness, bereavement, technical issue with HMRC's systems) you can appeal with evidence; HMRC accepts reasonable excuse appeals in most genuine cases.

Q: Do I need an accountant or can I file Self Assessment myself?

Legally you can file Self Assessment yourself via gov.uk for free, most simple sole-trader returns (single income source, basic expenses) are realistic to self-file. An accountant adds real value when: your trading profit is above £40,000 (extraction-strategy decisions matter), you have multiple income streams (PAYE + self-employment + property + dividends), you've crossed the £90,000 VAT threshold, you're considering incorporation, or you have an HMRC enquiry. Expect to pay £400-£1,500/year for a typical sole-trader accountant; the cost is itself a deductible expense.

Q: How do payments on account work?

When your Self Assessment tax bill exceeds £1,000 for the first time, HMRC requires payments on account toward NEXT year's tax. Half the current bill is due 31 January (alongside the current bill); the other half is due 31 July. So your first January after crossing the threshold can hit with a double-bill: last year's balance + first payment on account. Adjust via Form SA303 if you expect next year's income to drop substantially. Payments on account don't apply if more than 80% of your tax is collected via PAYE.

Q: I'm a Ltd Co director, can I invest in another SEIS company for the relief?

Yes, provided you're an EXTERNAL investor in the SEIS company (not an employee or substantial-interest holder there). The fact you're a director of YOUR OWN Ltd Co doesn't disqualify you from SEIS on a separate investment in someone else's qualifying company. The 30% substantial-interest test applies to the SEIS COMPANY specifically, you can't be an employee + can't hold over 30% of its share capital. Owner-directors are a common SEIS investor demographic: they have income to shelter (50% relief), have CGT exposure from their own business (reinvestment relief), + understand the risks of early-stage investment. Always check the SEIS company has HMRC Advance Assurance + has issued a valid SEIS Certificate (Form SEIS3) before claiming.

Q: I invested £30,000 in a friend's SEIS startup that just went bust 2 years later, what happens to my reliefs?

Mixed outcome. The 50% income tax relief (£15,000 cash-in-hand reduction to your tax bill in the year of investment) is preserved provided you claimed it correctly + held for the minimum period, and a failed SEIS company doesn't trigger relief withdrawal. The 3-year CGT exemption period is moot because there's no gain to exempt (the shares have collapsed to nil value). The valuable secondary relief is SEIS LOSS RELIEF: you can claim the realised capital loss against either income tax (sideways) or capital gains tax in the year of write-off. Loss is calculated as: original cost minus disposal proceeds minus any income tax relief already received. £30,000 cost - £0 proceeds - £15,000 income tax relief = £15,000 loss available for sideways relief at marginal rate. Total combined recovery on a £30,000 failed investment: £15,000 (initial relief) + up to £7,500 (45% additional-rate loss relief) = £22,500, leaving real loss of £7,500 on £30,000 risked.

Q: Can I carry back SEIS relief to the previous tax year?

Yes, SEIS allows ONE-YEAR CARRY-BACK of relief. An investment made in 2025/26 can elect to be treated for income tax relief purposes as if made in 2024/25 (provided the £200,000 annual limit isn't exceeded in either year). Useful when your previous year had higher income (e.g. dividend extraction crystallised in 2024/25 + you want to recover tax paid then). Make the carry-back election on your Self Assessment return for the year of investment. The CGT 3-year clock for the gain exemption still starts from actual issue date, not the elected relief year.

Q: What's the difference between SEIS reinvestment relief and SEIS income tax relief?

They're separate reliefs that often combine on the same investment. **Income Tax relief**: 50% × investment amount = tax reducer applied against current-year income tax liability. **Reinvestment Relief (CGT)**: if you sell another asset + reinvest the gain into SEIS shares within the qualifying period, 50% of the gain (up to £100,000/year) is permanently exempt from CGT (not deferred, totally exempt). On a £50,000 SEIS investment, an investor reinvesting a £40,000 gain from a buy-to-let sale gets BOTH: 50% × £50,000 = £25,000 income tax relief + 50% × £40,000 = £20,000 of the gain permanently CGT-exempt. Combined relief: £25,000 + (20% or 24% × £20,000 of avoided CGT depending on rate), potentially £29,800 of tax relief on a £50,000 investment, before any future CGT exemption on disposal of the SEIS shares themselves.

SEIS offers the most generous income tax relief of any UK investor relief scheme: 50% of the amount invested in qualifying early-stage trading companies, up to £200,000 per individual per tax year (doubled from £100,000 in April 2023). Relief is given as a tax reducer that can reduce income tax liability to NIL for that year. Shares held for at least 3 years generate completely CGT-EXEMPT gains on disposal (provided income tax relief was claimed). SEIS reinvestment relief is the second layer: if you reinvest a gain from any asset disposal into SEIS shares, 50% of the gain (up to £100,000/year) is PERMANENTLY exempt from CGT, not merely deferred. Investors cannot be employees of the company + must not hold more than 30% of share capital; the company must be early-stage with gross assets under £350,000 at investment + qualifying trading activity.

Last reviewed: 23 May 2026

Guidance, not advice. We explain the rules, we don't assess your situation. Always seek financial or tax advice from your accountant, or contact HMRC. Read our editorial scope →

What this relief is, in plain English

SEIS is the UK government's flagship relief for very early-stage company investment. It targets pre-revenue + just-launched businesses with gross assets under £350,000, deliberately calibrating its generosity to the high risk involved. The headline 50% income tax relief is unrivalled in mainstream UK tax: invest £200,000 in qualifying SEIS shares + get £100,000 of your income tax liability eliminated for that year (subject to having enough tax to relieve against). Three CGT mechanisms run in parallel. (1) Shares held 3+ years: disposal gain is fully CGT-exempt. (2) Reinvestment relief: 50% of any gain from any other asset reinvested into SEIS shares is permanently exempt from CGT (not merely deferred, the gain disappears). (3) Loss relief: if the SEIS company fails, the realised loss (net of income tax relief already claimed) can be set sideways against income tax at marginal rate OR against CGT. Combined, these mechanisms make SEIS one of the most asymmetric risk-reward propositions in UK personal finance, total downside on a £30,000 investment in a failed company is often around £7,500 (75% loss protection from various reliefs); total upside is uncapped capital appreciation that's entirely CGT-free.

How it works

50% income tax relief as tax reducer

Annual investment limit £200,000 per individual (doubled from £100,000 in April 2023). 50% × amount invested = tax reducer applied against the investor's income tax liability for the year. Tax reducer mechanic means relief can reduce income tax to NIL for that year (vs deductions which only reduce taxable income). Carry-back to previous year available, elect on Self Assessment. Requires SEIS3 certificate from the company (issued after HMRC compliance check, typically 1-4 months post-investment). Claim on Self Assessment SA101 supplementary pages.

CGT exemption after 3-year holding period

Shares held for at least 3 years from date of issue + income tax relief claimed + retained: any gain on disposal is COMPLETELY CGT-EXEMPT. No annual exempt amount used, no rate applied, the gain doesn't enter CGT computation at all. Disposal within 3 years triggers income tax relief WITHDRAWAL (relief clawed back) + the gain is fully taxable at normal CGT rates. The 3-year clock starts from actual share issue date, not from any elected carry-back year.

Reinvestment relief, 50% permanent CGT exemption

If you reinvest a gain from disposal of ANY asset into qualifying SEIS shares within the relevant window (broadly the same tax year), 50% of the gain (up to £100,000/year) is PERMANENTLY EXEMPT from CGT, not deferred, not rolled, just gone from the CGT computation. Worked example: sell buy-to-let with £40,000 gain → reinvest £30,000 of that gain into SEIS shares → £15,000 of the gain (50% × £30,000) is permanently exempt. The remaining £25,000 of the £40,000 gain remains taxable at the normal CGT rate.

Loss relief on failed investment

If the SEIS company fails + shares become worthless, the realised capital loss (net of income tax relief already received) can be set against either (a) other capital gains, or (b) income tax via sideways loss claim (s.131 ITA 2007). Loss calculation: original cost minus disposal proceeds minus income tax relief received = allowable loss. On a £20,000 SEIS investment with £10,000 income tax relief received, the allowable loss on total failure is £20,000 - £0 - £10,000 = £10,000, settable against income at marginal rate (45% × £10,000 = £4,500 additional recovery). Combined recovery: £10,000 + £4,500 = £14,500 on £20,000 invested = 72.5% loss protection.

Who qualifies

Individual UK taxpayer with sufficient income tax liability to absorb the relief (or carry-back available)
Investment in QUALIFYING SEIS company, early-stage trading company, gross assets <£350,000 at investment, <25 employees, raised <£250,000 total under SEIS lifetime, trading <3 years
Investor is NOT an employee of the SEIS company (directors permitted under limited 'business angel' director arrangements)
Investor + associates do NOT hold more than 30% of share capital, voting rights, or rights to assets on winding up
Shares are NEWLY ISSUED, fully paid in cash, no anti-avoidance arrangement, no pre-arranged exit
SEIS3 certificate received from company (typically 1-4 months post-investment, after HMRC compliance check)
Holding period of at least 3 years from share issue (or relief is withdrawn)

Interactions with other reliefs

EIS, Enterprise Investment Scheme

SEIS + EIS often combine on a 'SEIS first, then EIS' company funding round. SEIS covers the first £250,000 of company-lifetime relief at 50% income tax + 100% CGT exemption. After SEIS limits are reached, the same company can offer EIS investment at 30% income tax + CGT deferral. Investors can hold BOTH SEIS + EIS shares in the same company across different funding rounds, different £200k SEIS annual limit + £1m EIS annual limit apply separately on the investor side.

VCT, Venture Capital Trusts

Both offer 30% income tax relief (VCT) or 50% (SEIS), but very different vehicles. SEIS is DIRECT investment in a single company (high concentration risk, high upside). VCT is INDIRECT via a listed investment company holding a diversified portfolio (lower risk, lower concentration of relief mechanics). High-net-worth investors often hold both, SEIS for concentrated bets on specific founders, VCT for tax-efficient diversified exposure to UK SME equity.

BADR, Business Asset Disposal Relief

Different stages of the business lifecycle. SEIS reduces the cost of investing in someone else's startup. BADR reduces the CGT on selling your own qualifying business. The two reliefs can apply to the same individual at different times (founder + angel investor). No direct interaction on a single transaction, but the combination is the architecture for many serial entrepreneurs: build + exit your company under BADR → reinvest exit proceeds into other founders' companies via SEIS → repeat.

Pension Annual Allowance + Carry Forward

Both compete for the same 'gross income to shelter' optimisation problem for high earners. Pension contributions reduce taxable income (deductions); SEIS reduces income tax liability (tax reducer). Pension's tax-free growth is broader; SEIS's 100% CGT exemption + reinvestment relief is more powerful per pound deployed but concentrated in specific company risk. Many advisers recommend pension contributions to use the £60,000 annual allowance first + SEIS for income above that point, though personal risk tolerance + advice on specific SEIS companies is essential.

Common mistakes + audit triggers

Investing without confirming the company has HMRC Advance Assurance + the SEIS3 certificate will issue (some companies pitch as 'SEIS-eligible' but fail HMRC compliance check)
Holding the shares for less than 3 years (income tax relief withdrawn + CGT exemption lost)
Becoming an employee of the SEIS company within 3 years (relief withdrawal trigger)
Exceeding the 30% substantial-interest limit through subsequent investments or associate-holdings
Claiming relief for shares acquired second-hand (only newly-issued shares qualify)
Investing more than the company's £250,000 lifetime SEIS limit (excess gets no SEIS relief)
Confusing the £200,000 INVESTOR annual limit (your cap) with the £250,000 COMPANY lifetime limit (company's cap), both apply
Failing to keep evidence of the SEIS3 certificate + maintain records for HMRC inquiry (relief claim challengeable for 4-6 years after the tax year)

Worked example

Sanjay, Bristol - Higher-rate-taxpayer Ltd Co director + active angel investor in SEIS startups (2025/26)

Sanjay runs a profitable Ltd Co consultancy in Bristol + draws £75,000 in salary + dividends 2025/26 (basic + higher rate income, total income tax bill ~£18,000). He's also angel-investing in early-stage tech. In 2025/26 he invests £180,000 across 4 SEIS companies (£45,000 each). One of them is co-founded by his ex-colleague Aisha. Sanjay has NO substantial interest in any of these companies + is not an employee. He also sold a buy-to-let in 2025/26 with a £60,000 capital gain.

Calculation: **Step 1: Income tax relief on SEIS investment.** £180,000 × 50% = £90,000 tax reducer. But Sanjay's total income tax liability is only £18,000, relief is capped at £18,000 (you can't reduce below zero). **Step 2: Carry-back to 2024/25.** Sanjay elects to carry back £24,000 of the SEIS investment (£12,000 relief) to 2024/25 where he had higher dividend extraction + £15,000 income tax liability. This recovers £12,000 of tax paid in 2024/25. **Total income tax relief: £18,000 (2025/26) + £12,000 (2024/25 via carry-back) = £30,000 cash-in-hand recovery.** Remaining unused £48,000 of theoretical relief: WASTED (no carry-forward of unused SEIS relief beyond the previous year). **Step 3: CGT reinvestment relief on the buy-to-let gain.** £60,000 gain crystallised. Reinvest £60,000 of the SEIS investment trigger, 50% × £60,000 = £30,000 of the gain is permanently CGT-exempt. Remaining taxable gain: £60,000 - £30,000 - £3,000 (annual exempt amount) = £27,000 taxable at 24% (residential property higher rate) = £6,480 CGT. Without reinvestment relief: £60,000 - £3,000 = £57,000 × 24% = £13,680. **Reinvestment relief saving: £13,680 - £6,480 = £7,200.** **Step 4: Combined relief value.** Income tax cash recovery: £30,000. CGT saving: £7,200. **Total tax relief on £180,000 SEIS investment: £37,200 (20.7% effective subsidy).** **Step 5: Forward-year outcomes (if companies succeed).** If shares held 3+ years + companies do well, ANY gain on disposal is completely CGT-free. If one company 5×s the investment over 5 years: £45,000 invested → £225,000 disposal = £180,000 gain entirely CGT-free. **Step 6: Forward-year outcomes (if companies fail).** If one company fails: £45,000 cost - £0 proceeds - relief allocated ~£7,500 income tax = £37,500 allowable loss. Sideways at 40% marginal rate = £15,000 income tax recovery. Total recovery on that failure: £7,500 (initial relief) + £15,000 (loss relief) = £22,500. Net loss on £45,000: £22,500 (50% downside protection).

Statute reference: Income Tax Act 2007 Part 5A (ss.257A–257HJ), SEIS. HMRC manual: VCM30000 onwards (Venture Capital Schemes Manual).

Frequently asked questions

What happens if I miss the Self Assessment deadline?+

The Self Assessment deadline is 31 January (online filing) for the previous tax year. Miss it and HMRC apply an automatic £100 penalty. Beyond that: £10 per day from 3 months late (capped at £900), 5% of tax due at 6 months late, and another 5% at 12 months late, under Schedule 55 of the Taxes Management Act 1970. If you have a genuine reason (serious illness, bereavement, technical issue with HMRC's systems) you can appeal with evidence; HMRC accepts reasonable excuse appeals in most genuine cases.

Do I need an accountant or can I file Self Assessment myself?+

Legally you can file Self Assessment yourself via gov.uk for free, most simple sole-trader returns (single income source, basic expenses) are realistic to self-file. An accountant adds real value when: your trading profit is above £40,000 (extraction-strategy decisions matter), you have multiple income streams (PAYE + self-employment + property + dividends), you've crossed the £90,000 VAT threshold, you're considering incorporation, or you have an HMRC enquiry. Expect to pay £400-£1,500/year for a typical sole-trader accountant; the cost is itself a deductible expense.

How do payments on account work?+

When your Self Assessment tax bill exceeds £1,000 for the first time, HMRC requires payments on account toward NEXT year's tax. Half the current bill is due 31 January (alongside the current bill); the other half is due 31 July. So your first January after crossing the threshold can hit with a double-bill: last year's balance + first payment on account. Adjust via Form SA303 if you expect next year's income to drop substantially. Payments on account don't apply if more than 80% of your tax is collected via PAYE.

I'm a Ltd Co director, can I invest in another SEIS company for the relief?+

Yes, provided you're an EXTERNAL investor in the SEIS company (not an employee or substantial-interest holder there). The fact you're a director of YOUR OWN Ltd Co doesn't disqualify you from SEIS on a separate investment in someone else's qualifying company. The 30% substantial-interest test applies to the SEIS COMPANY specifically, you can't be an employee + can't hold over 30% of its share capital. Owner-directors are a common SEIS investor demographic: they have income to shelter (50% relief), have CGT exposure from their own business (reinvestment relief), + understand the risks of early-stage investment. Always check the SEIS company has HMRC Advance Assurance + has issued a valid SEIS Certificate (Form SEIS3) before claiming.

I invested £30,000 in a friend's SEIS startup that just went bust 2 years later, what happens to my reliefs?+

Mixed outcome. The 50% income tax relief (£15,000 cash-in-hand reduction to your tax bill in the year of investment) is preserved provided you claimed it correctly + held for the minimum period, and a failed SEIS company doesn't trigger relief withdrawal. The 3-year CGT exemption period is moot because there's no gain to exempt (the shares have collapsed to nil value). The valuable secondary relief is SEIS LOSS RELIEF: you can claim the realised capital loss against either income tax (sideways) or capital gains tax in the year of write-off. Loss is calculated as: original cost minus disposal proceeds minus any income tax relief already received. £30,000 cost - £0 proceeds - £15,000 income tax relief = £15,000 loss available for sideways relief at marginal rate. Total combined recovery on a £30,000 failed investment: £15,000 (initial relief) + up to £7,500 (45% additional-rate loss relief) = £22,500, leaving real loss of £7,500 on £30,000 risked.

Can I carry back SEIS relief to the previous tax year?+

Yes, SEIS allows ONE-YEAR CARRY-BACK of relief. An investment made in 2025/26 can elect to be treated for income tax relief purposes as if made in 2024/25 (provided the £200,000 annual limit isn't exceeded in either year). Useful when your previous year had higher income (e.g. dividend extraction crystallised in 2024/25 + you want to recover tax paid then). Make the carry-back election on your Self Assessment return for the year of investment. The CGT 3-year clock for the gain exemption still starts from actual issue date, not the elected relief year.

What's the difference between SEIS reinvestment relief and SEIS income tax relief?+

They're separate reliefs that often combine on the same investment. **Income Tax relief**: 50% × investment amount = tax reducer applied against current-year income tax liability. **Reinvestment Relief (CGT)**: if you sell another asset + reinvest the gain into SEIS shares within the qualifying period, 50% of the gain (up to £100,000/year) is permanently exempt from CGT (not deferred, totally exempt). On a £50,000 SEIS investment, an investor reinvesting a £40,000 gain from a buy-to-let sale gets BOTH: 50% × £50,000 = £25,000 income tax relief + 50% × £40,000 = £20,000 of the gain permanently CGT-exempt. Combined relief: £25,000 + (20% or 24% × £20,000 of avoided CGT depending on rate), potentially £29,800 of tax relief on a £50,000 investment, before any future CGT exemption on disposal of the SEIS shares themselves.

Last reviewed: 23 May 2026