Quote from korhonenmk >>

you cannot cast banishment on yourself

 The range of the spell is 60 feet. I feel like you would tend to be within 60 feet of yourself most of the time.

Material component: An item distasteful to the target.

Conclusion: Children can be banished using broccoli, and I can be banished using olives.

So who chooses where you go when you get banished back to your home plane? My character is extraplaner and resides on a different plane then the one he was born on. we are currently stuck in the feywild but my character has an amulate of the planes on my home plane. I was curious if my character chooses where he appears or is it purely random.

Quote from Laith_Amekir >>

So who chooses where you go when you get banished back to your home plane? My character is extraplaner and resides on a different plane then the one he was born on. we are currently stuck in the feywild but my character has an amulate of the planes on my home plane. I was curious if my character chooses where he appears or is it purely random.

Ultimately that would be a DM call. I don't believe the caster has any particular influence on the endpoint, simply based on the "a spell does what the description says and nothing more" principle.

This spell should have the teleportation tag. Part of it is practically plane shift. 

What happens if I banish a creature that has swallowed another creature? Does the swallowed creature get banished too, or is it freed?

Quote from Reubatina11 >>

What happens if I banish a creature that has swallowed another creature? Does the swallowed creature get banished too, or is it freed?

 Do you consider a creature, after its been consumed by another creature, a separate creature from the one that consumed it? Then, no.

Though, generally a creature that has been consumed by another creature is not going to be considered alive in most circumstances, and dead creatures are "objects."

So going off some of the comments below, if the target is a native of a different plane then they aren't incapacitated during the Banishment and if the spell ends early they just pop back to where they were?

Banishment. A minor nuisance until you’re on a plane you’re not native to.

This is the only way to exit a Demiplane other than Plane Shift btw

Can i Banishe my self and cast plane shift to go in materiel plan ?

Our fourth level elven war wizard can't select Banishment in D&D Beyond (or Dimension Door)...just not in the spell list when I scroll down under Add Spell. Any thoughts on why I can't see it (or Dimension Door)? Doesn't seem like I have to buy either of them from a source book in marketplace. :(

Quote from BensRPGPile >>

Our fourth level elven war wizard can't select Banishment in D&D Beyond (or Dimension Door)...just not in the spell list when I scroll down under Add Spell. Any thoughts on why I can't see it (or Dimension Door)? Doesn't seem like I have to buy either of them from a source book in marketplace. :(

I think you're getting character levels and spell levels mixed up. They're two totally separate things. Fourth-level spells (like this one, and like Dimension Door) are generally not available to characters until class level 7. A fourth level wizard has access to first-level and second-level spells. The class description has a table which shows which levels of spell slots are available at each class level.

This is an easy mistake to make and it's very frustrating to me that the same term is used for both of these things.

that is only if you are on your home plane, if you are on another as the original question asked, you simply pop into existence on your home plane.

An item distasteful to the target feels quite subjective. If I am in combat with you, would I be considered "distasteful" to you, and thus my own spell component? 

What would happen if you used this on a Monstrosity? Would it go to a demiplane?

Also could someone better explain the part about the target not coming back. ie requirements, est

thanks.  

Quote from Traveller_777 >>

What would happen if you used this on a Monstrosity? Would it go to a demiplane?

Also could someone better explain the part about the target not coming back. ie requirements, est

thanks.  

It depends on whether the monstrosity in question is native to the plane you're on when you cast the spell or not. Since monstrosities can come from a lot of different places, and you can cast this spell anywhere, there's no single answer to that question.

As for the part about the target not coming back, I think you're referring to this:

"If the spell ends before 1 minute has passed, the target reappears in the space it left or in the nearest unoccupied space if that space is occupied. Otherwise, the target doesn’t return."

Basically this means that the target returns if the spell ends early, but does not return if the spell lasts for its full duration of 1 minute. The spell could end early if you end it willingly or if you lose concentration on it for any reason.

This seems a very powerful spell for a sea battle on a moving ship. How would you interpret the returning to the same space if the ship is moving? Would the person return to the same place on the ship or in the air behind the ship and fall in the water?

Quote from Rosoro >>

This spell is OP. Parties routinely banish the boss mob, kill all minions, then dispatch the boss when it reappears.

House rules - Creatures can be banished back to the plane from where they came. The slot is spent and spell fails on a creature native to the plane in which it is cast.

 Playing smart is not "OP". 

Use it as backup discount Feather Fall. Falling friend? cast banishment on them as they get close to the ground. Then poof, return them.  Does the energy of their fall remain with them when they are gone? If so, then that opens up all kinds of fun uses, too.