What are SEIS1 and SEIS3 forms?
By SuLe · Updated 9 May 2026
SEIS1 is the compliance statement your company submits to HMRC after the share issue, confirming the SEIS conditions are met; SEIS3 is the certificate you then give each investor so they can claim their 50% income tax relief. You can only submit the SEIS1 once the company has traded for 4 months or spent 70% of the money raised. EIS1 and EIS3 are the EIS equivalents.
Key facts
- SEIS1/EIS1 is the company's compliance statement to HMRC; SEIS3/EIS3 is the certificate investors claim with.
- The SEIS1 can be submitted after 4 months of trading, or once 70% of the SEIS money has been spent.
- Advance assurance alone gives investors nothing to claim — only a SEIS3 does that.
- SEIS money must be spent on the qualifying trade within 3 years of the share issue.
- SEIS relief is 50% of the amount invested, capped at £200,000 per investor per tax year.
What is the SEIS1 form?
The SEIS1 is your company's formal statement to HMRC that the share issue meets the SEIS conditions — the compliance statement. It is filed by the company, after the shares are issued, and it is the step founders most often forget in the post-round glow.
It cannot go in immediately. HMRC accepts a SEIS1 only once the company has been trading for 4 months, or has spent 70% of the money raised, whichever you reach first.
Filing it is not optional admin. Without an accepted SEIS1 there are no certificates, and without certificates your investors have no relief at all.
What is the SEIS3 form?
The SEIS3 is the certificate an individual investor uses to claim their relief. Once HMRC has reviewed the SEIS1 and authorised the company, you complete a SEIS3 for each investor showing their shares and the amount subscribed.
The investor then claims the 50% relief from HMRC — typically through their tax return, with their accountant steering the timing. The claim belongs to the investor; your job is to get the certificate into their hands quickly.
For EIS rounds the machinery is identical with different numbers on the forms: EIS1 from the company, EIS3 to the investor, 30% relief.
When exactly can we file the SEIS1?
At the first of two gates: 4 months of trading, or 70% of the money spent. A company that starts trading before the round can hit the 4-month gate quickly; a company deploying cash fast may hit 70% first. Either works.
The spending has to be real spending on the qualifying trade — remember the money must all be used for that trade within 3 years of the issue.
Diarise the gates on completion day. The single most common SEIS1 failure is simply nobody owning the date, and every week of drift is a week your investors cannot claim.
How is advance assurance different from the SEIS1?
Advance assurance comes before the raise; the SEIS1 comes after. Assurance is HMRC's non-statutory pre-clearance that a proposed issue should qualify — not mandatory, but most angels will not invest without it, and applications now need details of your expected investors.
Assurance produces no relief by itself. It exists to de-risk the round; the SEIS1 and SEIS3 are what turn the promise into money off your investors' tax bills.
| Step | Who files or holds it | When | What it does |
|---|---|---|---|
| Advance assurance application | The company, before the round | Before investors commit; most angels require it | Non-statutory HMRC pre-clearance that the issue should qualify |
| SEIS1 / EIS1 | The company, after the share issue | After 4 months of trading or once 70% of the money is spent | Compliance statement confirming the scheme's conditions are met |
| SEIS3 / EIS3 | Completed for each investor | After HMRC accepts the compliance statement | The certificate the investor uses to claim 50% (SEIS) or 30% (EIS) relief |
Do EIS1 and EIS3 work the same way?
Yes — same architecture, different scheme. The company files an EIS1 compliance statement, HMRC authorises, and investors claim their 30% relief with EIS3 certificates.
One ordering point matters if you are raising under both schemes. SEIS shares must be issued before EIS shares — same-day issues are a known trap, so issue the SEIS shares first and the EIS shares later, and keep the paper trail unambiguous.
Companies running both will file both compliance statements, and investors in both tranches will need the right certificate for each.
Worked example
Dev and Alicia's edtech startup, TutorLoop Ltd, completes a £150,000 SEIS round on 1 March, having started trading on 1 February. Their two gates: four months of trading takes them to 1 June, and 70% of the money is £105,000.
Hiring fast, they spend £105,000 on salaries and product by 12 May — so the spending gate opens first and the SEIS1 goes in that week. HMRC reviews it, authorises TutorLoop, and SEIS3 certificates go out to all three angels.
The largest angel subscribed £50,000, so her certificate supports a £25,000 claim — 50% — through her next return. The SEIS1 went in barely ten weeks after completion, because someone owned the dates.
Where founders go wrong
Treating advance assurance as the finish line
— it unlocks nothing; without a SEIS1 and SEIS3s your investors have no claim.Filing the SEIS1 before either gate is open
— wait for 4 months of trading or 70% of the money spent, whichever comes first.Sitting on the certificates
— investors cannot claim until SEIS3s reach them, and claims have time limits; check HMRC's current guidance.Issuing SEIS and EIS shares on the same day
— SEIS must come first; a same-day issue is a known and expensive trap.
Related questions
Can investors claim SEIS relief without a SEIS3?
No. The SEIS3 certificate is what an investor uses to make the claim, and it only exists once HMRC has accepted the company's SEIS1 compliance statement. Until you hand over SEIS3s, your investors' 50% relief is theoretical — however long ago they paid.
What happens if the company fails before filing its SEIS1?
Investors are usually stranded: no SEIS1 means HMRC will not authorise SEIS3 certificates, so nobody can claim income tax relief — and the loss-relief position worsens too. If trouble is coming, filing the SEIS1 while the gates are open protects your backers. [More: What happens to SEIS relief if my startup fails?]
How is advance assurance different from the SEIS1?
Advance assurance is HMRC's non-statutory pre-clearance before you raise — reassurance for investors, not relief. The SEIS1 is the statutory compliance statement after the shares are issued. Most rounds need both: assurance to close the money, SEIS1 to unlock the certificates. [More: How do I get SEIS/EIS advance assurance?]
Is there a deadline for investors to claim SEIS relief?
Yes — claims are subject to time limits measured by tax year, so SEIS3 certificates should reach investors promptly rather than sitting in a drawer. Check HMRC's current guidance for the precise window, and let each investor's accountant handle the timing of the claim.
SEIS paperwork is a relay: shares issued, gates tracked, SEIS1 filed, certificates out — and dropping the baton at any leg leaves your investors with nothing to claim. A SuLe solicitor can set the timetable at completion and make sure the compliance statement says what HMRC needs to see. Book a free SEIS/EIS readiness call and keep the relief you promised deliverable.
Keep reading: How do I get SEIS/EIS advance assurance? · How long does SEIS advance assurance take? · Is my startup eligible for SEIS? · What happens to SEIS relief if my startup fails? · What is an SH01 and when must I file it?
Primary sources: HMRC — Apply to use the Seed Enterprise Investment Scheme · HMRC — Apply to use the Enterprise Investment Scheme · HMRC — advance assurance for venture capital schemes
