Vosaltres teniu l'IBAN.

Vosaltres is the informal plural form of you in Catalan.

English uses you for:

• one person
• more than one person
• informal or formal situations

Catalan separates these more clearly:

• tu = you (one person, informal)
• vosaltres = you (more than one person, informal)
• vostè / vostès = formal you

So vosaltres is used when speaking to two or more people in a casual or normal setting.

Because the verb has to agree with vosaltres.

The infinitive is tenir = to have.
In the present tense, it changes depending on the subject:

• jo tinc
• tu tens
• ell/ella/vostè té
• nosaltres tenim
• vosaltres teniu
• ells/elles/vostès tenen

So with vosaltres, the correct form is teniu.

Yes. Very often, Catalan leaves out the subject pronoun because the verb ending already shows who the subject is.

So Teniu l'IBAN is perfectly natural.

Including vosaltres can add:

• emphasis
• contrast
• clarity

For example, if you want to stress that you all have it, then vosaltres is useful.

It is informal.

If you want to address a group more formally, Catalan usually uses:

• Vostès tenen l'IBAN.

So the difference is:

• vosaltres teniu = informal plural
• vostès tenen = formal plural

Because the singular masculine article el becomes l' before a word that begins with a vowel sound.

So:

• el
  • IBAN → l'IBAN

This is the normal apostrophe rule in Catalan.

Similar examples:

• l'aigua
• l'amic
• l'hotel

Because Catalan often uses the definite article where English would not.

In English, you might say simply IBAN in some contexts. In Catalan, it is very natural to say l'IBAN when referring to a specific IBAN that both speakers know about.

This is common with:

• documents
• codes
• identifiers
• specific items being discussed

So the article here sounds normal and idiomatic.

A rough English-friendly approximation is teh-NEE-oo or tuh-NEE-oo.

A few useful points:

• the stress is on -ni-
• the final u is not strongly separated; it often sounds like a quick glide
• in Central Catalan, it is roughly tə-NIW

So it is not pronounced like English ten you.

This is the normal, neutral word order:
subject + verb + object

But Catalan word order is fairly flexible, especially for emphasis.

For example:

• Teniu l'IBAN. = very natural, with the subject omitted
• L'IBAN el teniu vosaltres. = emphasizes that you are the ones who have it

So the given sentence is standard and straightforward, but not the only possible order.