Where SEIS Eligibility Trips Founders Up Most Often
Seven avoidable mistakes that cost founders assurance and investors relief, in order of how often they actually happen.
In this article
Most SEIS failures are not exotic. The same handful of avoidable SEIS eligibility mistakes cost founders their advance assurance, or worse, cost their investors relief after the money is in. Having watched rounds from the inside, here is where eligibility actually trips people, in rough order of frequency.
1. Misreading the three-year clock
Founders count from incorporation; the rules count from first commercial sale. Sometimes that helps (an old shell, a young trade) and sometimes it wounds (a trade bought from a predecessor started the clock years ago). Every messy history needs checking before anyone mentions SEIS to an investor.
2. Taking the money before issuing the shares
Cash lands in the account in March, shares are issued in June, and suddenly there is an argument about what the March money was. Loans do not qualify. Issue shares against cleared funds, promptly and in that order, and the argument never exists.
3. The wrong instrument
Convertible loan notes do not qualify for SEIS, full stop. Advance subscription agreements can, but only when drafted as genuine advance subscriptions: short longstop, no interest, no refund. A US-style SAFE copied off the internet is how a round quietly disqualifies itself.
4. Tranches that break the asset test
Gross assets must be under £350,000 immediately before each issue. Bank a first close of £150,000 and the company may carry itself over the line before the second close. Sequencing and timing of issues are not clerical details; they are the test itself.
5. Family money and the 30% line
Parents, children and spouses aggregate with each other for the connection test. The proud parent taking 35% is connected; so is a founder’s spouse topping the family holding over the line. The relief disappears precisely for the investors most emotionally invested.
6. Forgotten grants
Certain de minimis state aid counts against the £250,000 SEIS lifetime cap. The innovation grant from two years ago can shrink the round you promised, and it is far better to discover that before the term sheet than after.
7. Drift inside the three-year window
Eligibility is a course to hold, not a gate to pass. Returning value to an investor, listing, being acquired, or leaning into an excluded activity within three years can claw back relief retrospectively. Investors forgive failure; they do not forgive clawbacks caused by carelessness.
The pattern behind all seven
Every one of these is cheap to catch early and expensive to catch late, which is the entire case for doing the eligibility checks properly, running the checklist, applying for advance assurance before closing anyone, and paying a professional for an hour at the first ambiguous answer.
Why these mistakes persist
None of these traps is secret, so why do smart founders keep walking into them? Because SEIS paperwork happens at exactly the moment founders have the least attention to spare: mid-raise, half the round soft-circled, product on fire. The rules reward sequence and patience precisely when the job demands speed, and the errors are invisible on the day they are made, surfacing only when a certificate fails or a clawback letter arrives eighteen months later. Which is the argument for systems over vigilance: the checks below take half an hour and do not rely on anyone being calm.
Three near-misses that follow the seven
- 8. Drifting from the assured plan. Assurance describes a specific raise. Change the class, the amount or the trade and close anyway, and the letter everyone is relying on describes a different company. Update HMRC or reapply; five days of patience beats a clawback.
- 9. Filing the SEIS1 early. Four months of trading and 70% of the spend are gates, not guidance. An early compliance statement bounces, and the resubmission queue is where investor goodwill goes to age.
- 10. Sitting on the SEIS3s. Once HMRC authorises, certificates are the founder’s job. Every month they sit unissued is a month investors cannot claim, and they remember it at the next round.
If you are the investor reading this
Every mistake above lands on you, so screen for them: ask when the trade first sold, how the round is sequenced against the asset test, what instrument you are signing, who else is over 30% with family counted, and who files the paperwork. Founders who answer quickly have done the eligibility work; founders who bristle have not. The wider due diligence view is in the reliefs guide.
The thirty-minute pre-round audit
Before any investor conversation, sit down with the company’s actual documents and answer, in writing: first commercial sale date and the evidence for it; FTE count today; gross assets today and immediately before each planned close; SEIS raised to date plus counted state aid; the instrument you are using and why it qualifies; every planned investor over 10% with family aggregation checked; and who, precisely, files the SEIS1 and when. Thirty minutes, one page, and five of the seven mistakes above become impossible. The checklist version pins it to the wall, and the full guide explains any line that stings.
