Samayvik Labs' two co-founders each hold 40 lakh shares on four-year vesting with a one-year cliff and monthly vesting after. One leaves after 18 months. How many shares does she keep, what happens to the rest, and how would double-trigger acceleration change the answer in a sale?

She keeps 15 lakh shares, 18/48 of her 40 lakh, and the other 25 lakh go back to the company at the nominal price the shareholders' agreement sets. The cliff vested 10 lakh at month 12 and each month after added 0.83 lakh. Acceleration does not help her: double-trigger needs both a sale and a dismissal, and she left voluntarily before any sale. For a founder still there when the company sells at month 30, double-trigger would vest her remaining 15 lakh only if the buyer let her go.

Two friends who open a restaurant and split it fifty-fifty have a problem if one walks out after a few months: he still owns half of a business the other will spend years building. Vesting fixes that by making each founder earn the shares over time: 40 lakh over 48 months is 0.83 lakh a month, but none of it vests until month 12, when a year's worth, 10 lakh, arrives at once. The cliff protects the company against a founder who leaves in the first year with a slice of the company. After it, vesting runs monthly. At month 18 she has 10 lakh from the cliff plus 6 months at 0.83 lakh, 15 lakh: 18/48 of her shares.

In India founders usually hold their shares outright, so vesting is a promise in the shareholders' agreement rather than a feature of the shares. The agreement typically lets the company, the other founder or a nominee buy back the unvested shares at face value or the original issue price, so she receives almost nothing for the 25 lakh and keeps the 15 lakh she earned. The route used, a company buyback, a transfer to the remaining founder or a transfer into the option pool, has company-law and tax consequences, and the reader should confirm the current rules with counsel rather than rely on a template.

The effect on the cap table depends on that route. If the 25 lakh are bought back and cancelled, shares in issue fall from 1 crore to 75 lakh: she holds 20% for her 18 months, and the founder who stays rises from 40% to 53.3%. If they go into the option pool instead, the stayer remains at 40% but the company has 25 lakh shares to offer the person who replaces her, which is usually the better use. Without vesting she would have kept all 40 lakh, 40% of the company, for 18 months of work: the dead equity that makes the next investor walk away.

Acceleration makes unvested shares vest early when something happens. Single-trigger vests them on one event, the sale itself. Double-trigger needs two events: a sale and then the founder being let go without cause, usually within a set period after it. It does nothing for the co-founder who left: she resigned, and there was no sale. Take the founder who stays and suppose the company is sold at month 30. She has vested 25 lakh and has 15 lakh unvested. Single-trigger hands her all 15 lakh at the closing, whether she stays or not. Double-trigger leaves them vesting under the buyer, and vests them all only if the buyer dismisses her; a 50% double-trigger would vest 7.5 lakh, taking her to 32.5 lakh.

Why investors and buyers prefer double-trigger: a buyer pays for a team, and single-trigger lets the founder collect every share on the day of the sale and leave the next morning. Double-trigger protects the founder against being sold and fired, and protects the buyer against paying for a team that walks. The limitation of the arithmetic is that it assumes a clean resignation; disputes over whether a departure was for cause, or a good leaver versus bad leaver clause that changes the buyback price, are where these cases actually get fought.