Ya he cambiado mi domicilio en el ayuntamiento porque me mudé el mes pasado.

In Spain, he cambiado (the pretérito perfecto) is very commonly used for a past action that is seen as connected to the present or relevant now.

So Ya he cambiado mi domicilio suggests:

• the change has already been done
• the result matters now

The word ya reinforces the idea of already.

In much of Latin America, many speakers would more naturally say ya cambié mi domicilio. In Spain, ya he cambiado sounds very normal.

This is a very common question, especially for learners of Spanish from Spain.

The difference is mainly about how the time is presented:

• Ya he cambiado mi domicilio
  No finished past time is stated here. The action is presented as relevant to the present.

• porque me mudé el mes pasado
  El mes pasado is a clearly finished past time period, so Spanish from Spain normally uses the pretérito indefinido: me mudé.

This contrast is very typical in Peninsular Spanish:

• Este mes he trabajado mucho.
• El mes pasado trabajé mucho.

So the sentence mixes the two tenses for a good reason.

Domicilio is a somewhat formal word for address or official place of residence.

In this sentence, it does not mean just any place you live in a casual sense. It refers more to your registered address for administrative or legal purposes.

That is why domicilio fits well with en el ayuntamiento, because dealing with the town hall is an official context.

Sometimes yes, but they are not always identical.

• dirección = address in general
• domicilio = residence/address in a more formal, legal, or administrative sense

In everyday situations, dirección is very common:

• ¿Cuál es tu dirección?

In official paperwork, domicilio is especially common:

• cambio de domicilio
• domicilio fiscal
• domicilio habitual

So in this sentence, domicilio sounds more appropriate because the context is administrative.

Because en el ayuntamiento indicates where the change was done: at the town hall.

• en = in / at
• al = to the

So:

• He cambiado mi domicilio en el ayuntamiento = I changed my address at the town hall.
• Fui al ayuntamiento = I went to the town hall.

If you used al ayuntamiento here, it would sound more like movement toward the building, not the place where the administrative action happened.

In Spain, el ayuntamiento is the town hall or local council of a municipality.

It is the local government office where people handle things like:

• registration
• address changes
• local documents
• municipal procedures

So this sentence sounds very specifically Spanish, because changing your registered address with el ayuntamiento is a familiar bureaucratic idea in Spain.

Very likely, yes.

In Spain, when someone moves, they often need to update their details on the padrón municipal. That process is commonly called:

• empadronarse
• cambiar el empadronamiento
• cambiar el domicilio en el padrón

So even though the sentence says he cambiado mi domicilio en el ayuntamiento, many Spanish speakers would understand it as a municipal registration/address-update process.

A more specifically bureaucratic version might be:

• Ya he cambiado mi domicilio en el padrón del ayuntamiento.
• Ya me he empadronado en mi nueva dirección.

Because mudarse is the standard verb for to move house / move home.

• mudarse = to move to a new home
• mudar without the reflexive pronoun usually means something else, or sounds formal, literary, or different in meaning

Examples:

• Me mudé a Madrid. = I moved to Madrid.
• Nos mudamos el año pasado. = We moved last year.

So me mudé is the normal everyday way to say I moved in the sense of changing residence.

Ya means already here, but it also gives a sense of completion.

Compare:

• He cambiado mi domicilio. = I have changed my address.
• Ya he cambiado mi domicilio. = I have already changed my address.

It often implies:

• the task is finished
• maybe it was something that needed to be done
• the speaker is reporting progress or completion

So ya makes the sentence sound more like That’s done now.

Spanish often uses possessives normally and naturally in cases like this, especially in official or practical contexts.

So mi domicilio is completely standard.

Also, in administrative language, Spanish often likes to state the noun clearly:

• mi domicilio
• mi dirección
• mis datos
• mi residencia

It would sound incomplete or strange here to omit it.

Because in Spanish, a possessive like mi usually replaces the article.

So you say:

• mi domicilio not
• el mi domicilio

The same pattern applies to:

• mi casa
• tu coche
• su nombre

This is different from some older forms of Spanish or other languages, but in modern standard Spanish, the article is not used before a normal possessive in this structure.

Because porque is used to give a reason: because.

• porque = because
• por qué = why

So here:

• ...porque me mudé el mes pasado = ...because I moved last month

Compare:

• ¿Por qué cambiaste tu domicilio? = Why did you change your address?
• Lo cambié porque me mudé. = I changed it because I moved.

This is one of the most common spelling distinctions learners need to master.

Because el mes pasado is the normal Spanish way to say last month.

In Spanish, many time expressions use this pattern:

• la semana pasada
• el año pasado
• el mes pasado

Putting pasado before the noun is generally not the normal choice in this expression.

So:

• el mes pasado = correct and natural
• pasado mes = unnatural here

Yes, Spanish word order is flexible, but some orders sound more natural than others.

The most natural version here is:

• Ya he cambiado mi domicilio...

Other possibilities are grammatically possible, such as:

• He cambiado ya mi domicilio...
• He ya cambiado... → not correct

Placing ya before the auxiliary verb, as in ya he cambiado, is very common and natural in everyday Spanish.

It is understandable and natural, but it leans slightly formal because of domicilio and the administrative context.

• domicilio sounds more official than dirección
• ayuntamiento places the sentence in a bureaucratic setting

A less formal everyday version might be:

• Ya he cambiado mi dirección en el ayuntamiento porque me mudé el mes pasado.

But the original sentence is perfectly fine, especially if someone is talking about official paperwork.