There are two common types of vesting acceleration, which are often listed as change of control provisions:
Single Trigger Acceleration
This means that upon change of control (e.g. acquisition, merger, sale) the holder will immediately vest all remaining stock. If a change of control provision exists, this is most commonly given to employees.
Double Trigger Acceleration
This means that upon change of control (e.g. acquisition, merger, sale) the holder will continue vesting normally until terminated from the new entity, and will then immediately vest all remaining stock. This is most commonly reserved for executives.
On Gust Equity Management
This is an optional part of every vesting schedule, and assumes 100% of the remaining balance is subject to acceleration. In some cases the acceleration is partial, and we'll soon have the ability to track the many nuances that accompany change of control provisions.