Adjuntamos la declaración responsable, pues es obligatoria.

Adjuntamos is the 1st person plural present tense of adjuntar (to attach, to enclose).

In formal Spanish, the present tense is often used in emails, letters, and administrative writing to mean something like:

• we attach
• we are attaching
• please find attached

So Adjuntamos la declaración responsable is a very natural formal way to say that the document is being included with the message or application.

Spanish usually does not need subject pronouns because the verb ending already shows who is doing the action.

• adjunto = I attach
• adjuntas = you attach
• adjuntamos = we attach

Because -amos clearly shows we, Spanish normally leaves out nosotros unless the speaker wants emphasis or contrast.

So Adjuntamos... sounds more natural than Nosotros adjuntamos... in most contexts.

In Spain, declaración responsable is often a fixed legal/administrative expression. It is not just a literal combination of two ordinary words.

It usually refers to a formal statement/declaration in which a person declares that certain information is true or that they meet certain legal requirements.

So learners should treat it as a set phrase used in bureaucracy, applications, official procedures, and public administration.

Because declaración is a feminine noun in Spanish.

That means it takes:

• la declaration
• obligatoria mandatory/required

The article and adjectives must agree with the noun’s gender and number:

• la declaración
• la declaración responsable
• es obligatoria

Even though responsable looks the same for masculine and feminine in the singular, obligatoria changes form and clearly shows feminine agreement.

Because responsable is an adjective with one form for both masculine and feminine singular.

So you get:

• el documento responsable
• la declaración responsable

But in the plural it changes only for number:

• los documentos responsables
• las declaraciones responsables

Not all Spanish adjectives change for gender. Some, especially those ending in -e, often stay the same in masculine and feminine.

Here pues means something like:

• since
• as
• because

So the sentence means that the declaration is attached because it is mandatory.

However, pues and porque are not always interchangeable in every context.

In this sentence:

• Adjuntamos la declaración responsable, pues es obligatoria.

the word pues sounds formal and written, which fits an administrative sentence very well.

If you said:

• Adjuntamos la declaración responsable porque es obligatoria.

that would also be correct, but a little more neutral and less formal in tone.

When pues introduces an explanation or justification in formal writing, it is often preceded by a comma.

So:

• Adjuntamos la declaración responsable, pues es obligatoria.

This comma helps mark the second part as the reason or explanation.

With porque, a comma is usually not used in the same way:

• Adjuntamos la declaración responsable porque es obligatoria.

So the punctuation here matches the more formal connector pues.

Spanish uses ser for essential characteristics, classification, or general statements, and estar for states, conditions, or locations.

Here obligatoria means mandatory/required by rule, which is seen as a general characteristic of the document in this context, so Spanish uses ser:

• es obligatoria = it is mandatory

Using estar obligatoria would sound wrong here.

Obligatoria agrees with la declaración responsable, which is:

• singular
• feminine

So the adjective must also be singular feminine:

• la declaración ... es obligatoria

Compare:

• el formulario es obligatorio
• la declaración es obligatoria
• los formularios son obligatorios
• las declaraciones son obligatorias

Normally, no. Adjuntamos is present tense, so it usually means:

• we attach
• we are attaching

If you want we attached, Spanish would normally use a past tense, such as:

• adjuntamos can technically also be the preterite form of some -ar verbs in spoken language without written accent distinction, but in standard written Spanish the past form is adjuntamos too, and context tells you which meaning is intended.

In this sentence, the context is clearly a formal message accompanying a document, so the natural reading is present: we attach.

This is one of those cases where Spanish spelling gives the same written form for two tenses, but the situation usually makes the meaning obvious.

It is common, but especially in formal, administrative, email, and document-related contexts.

You will often see it in phrases like:

• Adjunto el archivo.
• Le adjuntamos la documentación.
• Se adjunta el formulario.

In casual conversation, people might sometimes use other wording depending on the situation, but adjuntar is extremely common in offices, applications, and email communication.

Yes. Formal Spanish often uses impersonal or passive-style wording. For example:

• Se adjunta la declaración responsable, pues es obligatoria.
• Adjuntamos la declaración responsable, ya que es obligatoria.
• Le adjuntamos la declaración responsable, pues es obligatoria.

These all sound natural in formal contexts, though the exact tone changes a little:

• Adjuntamos... = direct, formal
• Se adjunta... = impersonal, very administrative
• Le adjuntamos... = formal and directed to the recipient

Yes, this exact expression is especially associated with Spanish administrative/legal usage in Spain.

A learner of Spanish from Spain should recognize it as a common bureaucratic term. Even if other Spanish-speaking countries may have similar documents, the phrase declaración responsable is particularly familiar in Spain’s official procedures.

So in this sentence, the vocabulary strongly suggests a formal Spanish administrative context.