El seu passaport és a la bossa.

In Catalan, possessives are usually used with the definite article:

• el meu llibre = my book
• la seva casa = her/his house
• els nostres amics = our friends

So el seu passaport is the normal pattern. English usually does not use the before a possessive, but Catalan generally does.

Seu is a possessive that can mean several things depending on context:

• his
• her
• its
• their
• sometimes formal your

Catalan often leaves that information to context, so seu by itself does not tell you who the owner is.

Because the possessive agrees with the thing possessed, not with the owner.

Here, passaport is masculine singular, so you use seu.

Compare:

• el seu passaport = his/her/their passport
• la seva bossa = his/her/their bag
• els seus documents = his/her/their documents
• les seves claus = his/her/their keys

So the form changes to match the noun, not the person who owns it.

Catalan often uses ser to state a simple location:

• El seu passaport és a la bossa.

That is completely natural.

In everyday Catalan, you may also hear està in similar sentences, especially if the speaker is emphasizing where something currently is. But for a straightforward statement of location, és is very normal.

The accent is part of the correct spelling of the verb form és = is.

It also helps distinguish it from es, which is a pronoun:

• és = is
• es = himself/herself/itself, or part of a pronominal verb

For example:

• És aquí. = It is here.
• Es diu Marta. = Her name is Marta / She is called Marta.

So the accent really matters in writing.

Because Catalan a is broader than English to.

With location, a can correspond to:

• in
• at
• sometimes on

depending on the context.

So in this sentence, és a la bossa means the passport is in the bag.

If you want to make inside especially clear, you could also say:

• És dins de la bossa.

Because bossa is feminine.

In Catalan:

• a + el = al
• a + la = a la

So:

• al cotxe = in/to the car
• a la bossa = in/to the bag

There is no contraction here because la is feminine.

Because Catalan normally uses an article with a noun like this when referring to a specific, identifiable thing.

So la bossa means the bag.
Here, it is understood to be a particular bag, not just any bag.

If you meant a bag in a non-specific way, you would use:

• una bossa

For example:

• És en una bossa. = It is in a bag.

For a neutral everyday sentence, el seu passaport is the normal choice.

Putting the possessive after the noun, as in el passaport seu, is much less common and usually sounds marked, emphatic, or literary.

So for ordinary speech and writing, it is best to use:

• el seu passaport