What is founder vesting and how does it work in the UK?
By SuLe · Updated 20 May 2026
Founder vesting means each founder earns the right to keep their shares over time — typically four years — so someone who quits after six months cannot walk away with a quarter of the company. In the UK it works as reverse vesting: you legally own all your shares from day one, but the company or remaining shareholders can buy back the unvested portion at nominal value if you leave.
Key facts
- The typical founder schedule is 4-year vesting with a 1-year cliff, vesting monthly after the cliff.
- UK founder vesting is reverse vesting: you hold every share from day one, and unvested shares can be bought back at nominal value if you leave.
- The mechanics live in your shareholders' agreement or articles of association — not in an option scheme.
- Founders acquiring restricted shares should sign a section 431 election (ITEPA 2003) within 14 days; it cannot be made late.
- Founder share issues are employment-related securities, reportable to HMRC on the annual ERS return by 6 July after the tax year.
Why do founders need vesting at all?
Vesting protects the founders who stay from the founder who leaves. Equity is payment for years of future work, and vesting makes sure it is actually earned rather than banked on day one.
Without it, a co-founder who walks out in month six keeps their full stake while everyone else spends years making it valuable. That dead equity then poisons every later conversation — with new hires, with investors, and between the remaining founders.
The 4-year, 1-year-cliff pattern is the standard founder arrangement precisely because every startup faces the same risk. Signing up to it early is far easier than negotiating it after someone has already half-left.
How does founder vesting work mechanically in the UK?
UK founders do not receive shares gradually — they subscribe for all of them at the start and are full shareholders from day one, on the register of members. This is reverse vesting: the schedule controls not what you get, but what can be taken back.
If a founder leaves part-vested, the unvested portion can be bought back, transferred or converted to deferred shares at nominal value — the share's face value, often a fraction of a penny, rather than what it is really worth.
None of this happens automatically. The machinery must be written into the shareholders' agreement or the articles of association; a vesting promise in an email or slide deck gives the company no enforceable way to recover a single share.
What is a typical founder vesting schedule?
Typically 4 years with a 1-year cliff: nothing vests in year one, 25% vests at the twelve-month mark, and the rest vests monthly until month 48. The cliff filters out early departures; monthly vesting afterwards keeps things fair in both directions.
When the clock starts is negotiable. It usually runs from incorporation or the shareholders' agreement, but founders who worked unpaid for a year before incorporating sometimes agree to backdate the start — a legitimate negotiating point, not a fiddle.
| If a founder leaves at… | Vested | Unvested (recoverable at nominal value) |
|---|---|---|
| Month 6 | 0% | 100% |
| Month 12 (the cliff) | 25% | 75% |
| Month 18 | 37.5% | 62.5% |
| Month 30 | 62.5% | 37.5% |
| Month 48 | 100% | 0% |
The illustration above assumes the typical 4-year, 1-year-cliff schedule. What happens to the vested column depends on your leaver provisions, not the vesting schedule itself.
What tax paperwork does founder vesting trigger?
Two HMRC deadlines, both unforgiving. First, shares subject to vesting restrictions are restricted securities: each founder should sign a section 431 election under ITEPA 2003 within 14 days of acquiring them, which fixes the tax position so later growth is taxed as capital gain rather than employment income. There is no way to make the election late.
Second, shares issued to founders, directors or employees are employment-related securities. Acquisitions and events must be reported to HMRC on the annual ERS return by 6 July following the tax year.
Both are cheap to get right at the time and impossible to fix afterwards. Put them in the incorporation checklist next to the Companies Act 2006 filings.
What happens when a founder leaves part-vested?
The unvested shares go back at nominal value — that is the vesting bargain. The vested shares are governed by your leaver provisions instead: good leavers typically keep them or sell at market value, while bad leavers can be forced to sell at the lower of cost and market value.
Remember that shareholding and employment are legally separate. If your documents contain no vesting and no leaver provisions, a departing founder simply keeps everything, however early they leave.
Worked example
Maya and Stefan incorporate a payments-reconciliation startup with 1,000,000 ordinary shares of £0.001 each — 500,000 apiece — and adopt a shareholders' agreement with 4-year vesting, a 1-year cliff and monthly vesting thereafter. Both sign section 431 elections within 14 days of the issue.
At month 18 Stefan leaves amicably to return to employment, and the agreement treats him as a good leaver. He has vested 18/48ths of his stake — 187,500 shares — which he keeps.
His 312,500 unvested shares transfer to Maya at nominal value, £312.50, with no stamp duty because the price is below £1,000. Stefan exits holding 18.75% of the company instead of 50%; Maya, who is still building it, holds 81.25%.
Where founders go wrong
Skipping vesting because you trust each other.
Trust is exactly why you can sign fair terms now — wait until someone is halfway out of the door and every clause becomes a fight.Thinking vesting means the shares arrive later.
UK founder vesting is the reverse: you own everything from day one, and the documents must create the right to claw the unvested part back.Missing the 14-day section 431 window.
There is no late election, and the cost of missing it surfaces years later — as employment income tax on growth that should have been capital gain.Vesting without leaver definitions.
The schedule decides how many shares are safe; good and bad leaver terms decide the price of the rest. You need both.
Related questions
Is founder vesting the same as reverse vesting?
Yes, in substance. Reverse vesting is the mechanism UK founders use: you own all your shares from day one, and the unvested portion can be clawed back at nominal value if you leave. The label distinguishes it from option vesting, where shares only arrive as they vest. [More: What is reverse vesting?]
Why do vesting schedules have a cliff?
The cliff means nothing vests during the first period — leave in month 11 of a 1-year cliff and you keep nothing; stay to month 12 and a quarter vests at once. It stops someone who leaves within months from carrying a permanent slice of the company. [More: What is a vesting cliff?]
Do we need to tell HMRC when founder shares are issued?
Usually, yes. Shares issued to founders, directors or employees count as employment-related securities, and acquisitions must be reported on HMRC's annual ERS return by 6 July following the tax year. Separately, each founder should consider a section 431 election within 14 days of acquiring restricted shares. [More: What is a section 431 election and why does the 14-day deadline matter?]
What happens to my shares if I leave before I am fully vested?
Your unvested shares are bought back or transferred at nominal value. What happens to the vested portion depends on your leaver status: good leavers typically keep vested shares or sell them at market value, while bad leavers can be forced to sell at the lower of cost and market value. [More: What happens to a co-founder's shares if they leave?]
Should employee options vest on the same schedule as founder shares?
They often use a similar shape, but the mechanism differs: employees hold options and only receive shares as they vest and exercise, whereas founders hold shares from day one under reverse vesting. Employee schedules are set in the option scheme rules, not the shareholders' agreement. [More: What vesting schedule should employee options have?]
Vesting terms are short clauses with long consequences — the difference between a clean exit and a cap table carrying a ghost founder for years. A SuLe solicitor can draft or review your vesting and leaver provisions, and make sure the section 431 elections are signed in time. Get your founder documents reviewed — book a free consultation and lock the mechanics down while everyone is still friends.
Keep reading: What are good leaver and bad leaver provisions? · What should a shareholders' agreement include for a UK startup? · How should co-founders split equity in a UK startup? · What is a founders' agreement and do we need one? · Should advisors get equity — and how much? · Can we buy back shares from a co-founder who has left?
Primary sources: Companies Act 2006 · GOV.UK — Tell HMRC about your employment related securities schemes
