Rebate II: You restore 300Magicka or Stamina when one of your non-Ultimate Daedric Summoning abilities end. The resource returned is dictated by the ability's cost.
Rebate restores your Magicka or Stamina whenever one of your Daedric Summoning abilities ends with the resource restored based on the cost of the ability.
As of Update 9, the only way to unsummon a creature is to remove the skill from your skill bar. This can most easily be done via weapon swap, provided you don't have the same summoning skill in the same slot on both skill bars.
You may also unsummon them from your character screen. Scroll down to the creature and click remove effect.
Prior to Update 27, this passive only restored Magicka and only when one of your summons were killed or unsummoned.
Fixed an issue where this ability was not restoring magicka when a Daedric pet was de-summoned or died, and the magicka restore from this passive now scales with your level instead of your maximum magicka.
This passive now restores 150/300 Magicka or Stamina (determined by what the ability cost) when one of your Daedric Summoning non-Ultimate abilities end, rather than restoring Magicka when your Daedric Summoning pets died or were unsummoned.