The Founder's Vesting Cliff: A Field Guide

Vesting is a topic most founders learn about twice: once when their first investor hands them a term sheet, and once when they are about to lose money at an event they did not expect. This guide is for both moments.

We are going to walk through the mechanics, the tax treatment, the acquisition-time edge cases, and the parts of the standard NVCA template that most founders skim past. Where relevant we cite NVCA model legal documents, IRS guidance, and the Carta annual State of Private Markets reports — those three are the primary references for most of what follows. This is editorial guidance, not legal advice. Talk to a lawyer before any decision moves real money.

What vesting actually is

When a founder issues themselves stock at incorporation, the company simultaneously buys back the right to take that stock back if the founder leaves early. Vesting is the schedule on which the company loses that right. The most common schedule, used by the overwhelming majority of US-incorporated startups raising institutional venture capital, is four years with a one-year cliff. That means:

• For the first twelve months you own zero of your stock free and clear.
• On the first anniversary of the vesting commencement date, 25% becomes yours.
• Then the remaining 75% vests in equal monthly slices over the next three years.

If you leave before the one-year mark — voluntarily or otherwise — the company can repurchase 100% of your shares at the original price (which, for early-stage founders, is essentially zero).

The 83(b) election: do not skip this

When the company has the right to repurchase your unvested stock, the IRS by default does not consider you to own that stock for tax purposes. As it vests, the difference between the then-fair-market-value and what you paid is treated as ordinary income — at the worst possible time, in the worst possible form.

The fix is the Section 83(b) election. You file it within 30 days of receiving the restricted stock, and the IRS treats the whole grant as taxable at the date of grant. For a founder who buys their shares at par value at incorporation, that taxable event is approximately zero. From then on, any growth in value is capital gain, not ordinary income.

Miss the 30-day window and you cannot fix it. This is the single most expensive paperwork mistake a founder can make.

Single-trigger vs. double-trigger acceleration

Acceleration is what happens to unvested shares if the company is acquired or if you are terminated.

Single-trigger acceleration vests some or all of your remaining shares on a single event — typically the change of control. Acquirers do not love this. They are buying the company partially for the people, and a contract that lets the founders vest fully and leave on day one of integration makes them nervous.

Double-trigger acceleration requires two events: a change of control and a qualifying termination of the founder (usually defined as termination without cause or resignation for good reason). This is the standard most institutional investors will push for, and the standard most acquirers will live with. It is what the NVCA model employment-related agreements provide as the default.

The negotiation room on these terms is real but narrow. Senior founders at competitive Series A processes can sometimes secure six to twelve months of double-trigger acceleration. Founders at later rounds, or in less competitive processes, often get the standard NVCA template as-is.

What happens at acquisition

When the acquirer's term sheet lands, your vesting schedule will get rewritten. The new schedule typically includes:

• Conversion of your unvested startup shares into unvested acquirer shares, on a value-equivalent basis.
• A new vesting schedule that is often longer than what remained on your original (this is the integration plan dressed up as a vesting schedule).
• A retention bonus pool that, depending on the deal, may be larger than the equity proceeds for some founders.

If you negotiated double-trigger acceleration earlier, this is where it matters. A founder who is dismissed without cause in the integration period gets the acceleration. A founder who resigns because they do not like the new role usually does not, unless their employment agreement defines "good reason" carefully.

International founders: the bear traps

The standard US-centric vesting story breaks in several ways for founders who are not US tax residents:

• The 83(b) election has no analogue in most other tax systems. Some countries impose ordinary income tax on each vesting tranche; some defer the event to sale; some treat the entire grant as ordinary income at the date of grant. Get country-specific advice early.
• Acceleration may interact poorly with foreign tax credit rules in the founder's home country.
• "Good reason" definitions written for the US labor market may not map cleanly to foreign employment regimes.

The structures that work involve more paperwork than a US-only founder is used to, but they exist. The mistake is assuming the US template is portable.

A short checklist

If you take one thing from this guide, take this: at incorporation, file your 83(b). At your first priced round, read the acceleration provisions of your employment agreement carefully and negotiate them with informed counsel. At acquisition, do not sign anything before talking to a lawyer who has seen the inside of multiple acquisition processes.

The cost of getting these three moments right is a few thousand dollars in legal fees. The cost of getting them wrong runs into millions.

Sources

• NVCA model legal documents — nvca.org/model-legal-documents
• Carta State of Private Markets — carta.com/data
• IRS Form 83(b) and instructions — irs.gov/forms-pubs/about-form-83b

Try our free vesting calculator. Enter your grant, cliff, and expected exit price to see cliff date, monthly tranches, double-trigger acceleration payout, and 83(b) tax comparison — with a shareable URL for your co-founder or lawyer. → /tools/founder-vesting-calculator

From the editorial archive

• The Rule of 40 Is Dead: What SaaS Boards Actually Look At in 2026 — How boards evaluate the businesses those founders build.
• The Quiet Death of Third-Party Cookies — and What Replaced Them — A practitioner reference for the marketing side of the same startups.
• Vibe Coding's Quiet Revolution: A Year-One Audit — How the engineering side of those startups changed.