Tolling pauses the statute of limitations clock for a defined period, then resumes it once the qualifying condition ends. It is different from the discovery rule, which changes when the clock starts rather than pausing it mid-run.
The most common tolling condition is minority: if the injured party was under 18 at the time of the incident, most states pause the clock until they reach adulthood. Mental incapacity can have a similar effect.
Some states also toll the clock if the defendant leaves the state and cannot be served with a lawsuit, or in certain cases involving fraud or concealment by the defendant.
Tolling rules vary significantly by state and by claim type, so a deadline that looks expired on paper may still be viable if a tolling condition applied for part of that period.