¿Podría usted decirme si el descuento también vale para esta marca?

Podría is the conditional form of poder and makes the question more polite and less direct.

• ¿Puede usted decirme...? = Can you tell me...?
• ¿Podría usted decirme...? = Could you tell me...?

In English, could often sounds more courteous than can, and the same idea applies here. In shops, hotels, or other formal situations, podría is very common.

Usted is the formal word for you. It is used to show respect, especially with strangers, customers, staff, or older people.

It is not strictly necessary because the verb form already shows formality:

• ¿Podría decirme si el descuento también vale para esta marca?

This means the same thing. Including usted adds emphasis or makes the formality more explicit.

Decirme means to tell me.

It is made of:

• decir = to tell / to say
• me = to me

In Spanish, object pronouns can attach to an infinitive:

• decirme = to tell me
• explicarme = to explain to me
• mostrarme = to show me

So:

• ¿Podría usted decirme...? = Could you tell me...?

You could also say:

• ¿Me podría usted decir...?

Both are correct.

Yes, si often means if, but it also means whether in indirect questions.

Here it introduces the idea of whether the discount also applies:

• decirme si... = tell me whether...

This is very common in Spanish:

• No sé si viene. = I don't know whether he is coming.
• Preguntó si estaba abierto. = He asked whether it was open.

Important: this si has no accent.
Sí with an accent means yes.

Here vale para means is valid for, applies to, or works for.

So:

• el descuento vale para esta marca = the discount applies to this brand

The verb valer often literally means to be worth, but in everyday Spanish it also has uses like:

• Esto no vale. = This isn’t valid / This doesn’t count.
• ¿Vale para estudiantes? = Does it apply to students?

In Spain, this use of valer is very natural and common.

Yes. Se aplica a esta marca is also correct and may sound slightly more formal or technical.

Compare:

• ¿El descuento vale para esta marca? = very natural, everyday speech
• ¿El descuento se aplica a esta marca? = a bit more formal or business-like

In a shop in Spain, vale para sounds very normal.

También means also / too, and its position is flexible, but here it naturally modifies the idea that the discount applies as well to this brand.

• si el descuento también vale para esta marca

This suggests that the discount applies to other things, and the speaker is asking whether it applies to this brand too.

Other placements are possible in Spanish, but this one is very standard and natural.

Because marca is a feminine noun in Spanish.

• la marca = the brand
• esta marca = this brand

So the demonstrative must agree with the noun:

• masculine singular: este
• feminine singular: esta

Examples:

• este producto = this product
• esta marca = this brand

El descuento means the discount.

• descuento is a masculine singular noun
• that is why it takes el

Examples:

• el descuento
• un descuento
• los descuentos

The sentence is asking about a specific discount, so el descuento is used.

It is clearly formal.

The main signs are:

• podría instead of a more direct form
• usted instead of tú

A more informal version would be:

• ¿Podrías decirme si el descuento también vale para esta marca?

Or even:

• ¿Sabes si el descuento vale también para esta marca?

The original sentence is very suitable for speaking to shop staff politely.

Yes. Spanish often omits words that are understood from context.

For example:

• ¿Podría decirme si el descuento vale para esta marca?
• ¿Vale el descuento para esta marca?
• ¿Este descuento vale para esta marca?

These are all possible, depending on how polite or explicit you want to be. The original version is a fuller, more courteous way of asking.

Spanish uses two question marks in written questions:

• ¿ at the beginning
• ? at the end

So:

• ¿Podría usted decirme si el descuento también vale para esta marca?

This helps the reader know from the start that the sentence is a question. English only marks the end, but Spanish marks both beginning and end.

It sounds polite, correct, and natural, especially in a shop or customer-service setting in Spain.

A native speaker in Spain might also say:

• Perdone, ¿este descuento también vale para esta marca?
• Disculpe, ¿el descuento vale también para esta marca?

Your sentence is slightly more formal and careful, but absolutely natural.