Performance Bonuses and Carryover Overage

Bruins just signed Bergeron to 1 year/2.5 with 2.5 performance bonus. Now I know that the bonus can go over the cap, however the cap hit would get rolled over to next year. But when does that activate? What’s the cutoff date for “ok, we’re rolling these over to next year” or “ok, Craig smith you’re gone, mike Reilly you’re gone, we are not rolling these over”.