How does Bardic Inspiration work with Passive Perception?

Question

Bardic Inspiration

You can inspire others through stirring words or music. To do so, you use a Bonus Action on your turn to choose one creature other than yourself within 60 feet of you who can hear you. That creature gains one Bardic Inspiration die, a d6.

Once within the next 10 minutes, the creature can roll the die and add the number rolled to one ability check, Attack roll, or saving throw it makes. The creature can wait until after it rolls the d20 before deciding to use the Bardic Inspiration die, but must decide before the DM says whether the roll succeeds or fails. Once the Bardic Inspiration die is rolled, it is lost. A creature can have only one Bardic Inspiration die at a time.

My question is quite simple: How does this work with Passive Perception?

Firstly since Passive Perception is an ability check I assume it is a valid use of Bardic Inspiration, but I have read many different interpretations on Passive Perception on here; including DM's doing it slyly, even pretending to make checks to keep people off guard.

Passive Perception is 'always on' so how would you handle this? Do you just add 3 (The rounded up average for the d6) to the check for 10 mins?

Answer 1

It doesn't help passive anything.

The key word here is Passive Perception. Think of it as the character's AC against stealth. It's there so that the DM doesn't have to ask for a Perception check any time someone is trying to sneak up on the party. To help emphasise the point, consider this line from the inspire ability.

The creature can wait until after it rolls the d20

You don't roll anything for a passive skill, so nothing for the inspire die to boost.

It helps with active rolls

What you can do however, is inspire someone who is actively rolling a Perception check. If your party thinks they need to actively look around you can maximize the roll by doing a few things at once.

First pick the person with the highest Perception skill. Then any other party member can preform the Help action, granting advantage on the roll. Then the bard inspires the character, adding the die into the pool. The end result will be a very high chance at a much higher roll than a normal Passive Perception.

Answer 2

No bardic inspiration on passive checks

So first, to confirm your assumptions:

Passive checks

A passive check is a special kind of ability check that doesn’t involve any die rolls.

So, passive perception is an ability check. However, not that second part: it doesn't involve ANY die rolls. I would argue that this could be argued to exclude the rolling of bardic inspiration die RAW. Note that it doesn't say "doesn't involve any d20 rolls".

Another hint that bardic inspiration is not meant to be used on passive ability checks comes from bardic inspiration itself:

The creature can wait until after it rolls the d20 before deciding to use the Bardic Inspiration die, but must decide before the DM says whether the roll succeeds or fails.

So, bardic inspiration seems to assume that there is a d20 roll involved here. Which may speak to the intended use of it.

That is the way I would rule it at my table, no bardic inspiration on passive checks.

And this of course makes sense in-fiction as well. Passive perception is passive. It is you character's ability to notice things when they aren't focusing on it. So it doesn't make sense that it would be able to be actively modified by something the player does in reaction to it.

Answer 3

Bardic Inspiration [..] can roll the die and add the number rolled to one ability check, Attack roll, or saving throw it makes (PHB 53)

A passive check is a special kind of ability check that doesn't involve any die rolls. Such a check can represent the average result for a task done repeatedly (PHB 175)

(all emphasis mine)

A passive check is not a roll a creature (or player) makes, but a representation of continuous effort. As such it is not one roll and you cannot apply Bardic Inspiration to your passive score.