How big and what type of punishment they receive will depend on how big the breach is. As discussed in this thread, Everton were potentially as much as £40m over the PL's profit and sustainability limits for the 3 year cycle to 20/21 when factoring in allowable losses and basic covid losses but escaped punishment as they successfully argued additional covid losses were the cause of that £40m. They claimed a total of £170m in covid losses which I'd guestimate was around £100m more than the basics (lost match day revenue and tv rebate) but nobody knows what number the PL actually accepted, only that they were happy with at least £40m(ish).
Everton's accounts for last season aren't filed yet however they're likely to show a sizeable loss, which will replace a £9m FFP profit from the 17/18 accounts. A £30m FFP loss would mean Everton needing to now prove close to £80m of additional covid losses over and above the basics.