El precio fijo no cambia en la factura.

Because precio is a masculine singular noun, and here it is being used with the definite article el.

In Spanish, the definite article is often used more than in English. So el precio fijo can mean the fixed price or refer to the fixed-price amount in a general, known context.

• el = masculine singular the
• precio = masculine singular noun

If you changed it to un precio fijo, it would mean a fixed price, which is less specific.

In Spanish, adjectives usually come after the noun.

So:

• precio fijo = fixed price

This is the normal order for a classifying or descriptive adjective. It tells you what kind of price it is.

Putting the adjective before the noun is less common and can sound literary, emphatic, or unnatural depending on the adjective. In this case, fijo precio would not be the normal wording.

Precio fijo is a common expression meaning a price that stays set and does not vary.

Depending on context, it can mean:

• fixed price
• set price
• sometimes flat rate

It is a standard phrase in Spanish, just like in English.

Because the subject is singular: El precio fijo.

The verb has to agree with the subject:

• el precio fijo → singular
• cambia → 3rd person singular

If the subject were plural, the verb would also be plural:

• Los precios fijos no cambian

Because cambiar here is being used as an intransitive verb meaning to change.

So no cambia means:

• it does not change
• it doesn’t change

Spanish normally prefers this simple active structure here.

No es cambiado would mean it is not changed, which is a passive structure. That is much less natural in this context.

So:

• no cambia = natural
• no es cambiado = grammatically possible in some contexts, but not the normal choice here

The present tense is often used in Spanish for general facts, regular situations, or standard policies.

So no cambia can mean:

• it doesn’t change
• it does not change

This sounds like a general statement about how the fixed price behaves on the invoice.

It is not necessarily about one single moment only. It can describe a rule or usual situation.

Here en la factura means on the invoice/bill or in the invoice, depending on how natural that sounds in English.

The preposition en is very common and can cover meanings like:

• in
• on
• at

In this sentence, it gives the context where the price does not change: on the bill/invoice.

Because en and de mean different things.

• en la factura = on/in the invoice
• de la factura = of/from the invoice

Here the idea is location or context, so en is the right choice.

If you said de la factura, it would suggest possession, origin, or relationship, not the place where the unchanged price appears.

It can mean either, depending on context, but in Spain factura often means invoice or an official bill, especially for services like electricity, phone, or business transactions.

Some useful distinctions in Spain:

• factura = invoice / official bill
• cuenta = bill at a restaurant
• recibo = receipt or payment slip, depending on context
• ticket = receipt

So factura here sounds like an invoice or formal bill.

Because it agrees with precio, which is masculine singular.

Spanish adjectives usually agree with the noun in gender and number:

• precio fijo = masculine singular
• tarifa fija = feminine singular
• precios fijos = masculine plural
• tarifas fijas = feminine plural

So fijo changes form to match the noun it describes.

Yes, a little, but not completely freely.

For example, you could say:

• El precio fijo no cambia en la factura.
• En la factura, el precio fijo no cambia.

Both are possible. The second version emphasizes en la factura a bit more.

But you normally would not move fijo before precio in standard Spanish. Precio fijo is the natural unit.

You could build a sentence with se cambia, but it would not mean exactly the same thing and would sound less natural here.

Compare:

• no cambia = it doesn’t change
• no se cambia = it is not changed / people do not change it

The version with se suggests an action done by someone, even if the someone is not named. The original sentence is simply describing the price as remaining unchanged.

So in this context, no cambia is the more natural choice.

Yes. Cambiar is a regular -ar verb.

Present tense:

• yo cambio
• tú cambias
• él/ella cambia
• nosotros cambiamos
• vosotros cambiáis
• ellos/ellas cambian

So cambia is the normal él/ella/usted form, matching el precio fijo.