El borrador de la declaración incluye los datos fiscales.

Because borrador is a masculine noun. In Spanish, noun gender does not always match the ending perfectly, although -o often signals masculine. Here, the noun is simply el borrador.

Also, borrador can mean:

• draft
• eraser

In this sentence, it means draft.

Here, borrador means draft — specifically, a preliminary version of a tax return.

In Spain, el borrador de la declaración is commonly used in tax contexts to mean the draft version prepared for you, often by the tax authorities.

De means of, so el borrador de la declaración literally means the draft of the declaration.

In natural English, that becomes the draft tax return or the draft declaration depending on context.

It is de la because:

• de = of
• la declaración = the declaration

There is no contraction here because de + la stays de la. Only de + el contracts to del.

Literally, yes, declaración means declaration. But in this context, in Spain, it usually refers to a tax return.

Very often, people shorten la declaración de la renta to simply la declaración when the tax context is clear.

So here, la declaración is best understood as the tax return.

Spanish often uses the definite article where English might leave it out.

So los datos fiscales means the tax details/data. In English, we might naturally say:

• tax information
• tax details
• the tax data

Spanish prefers the article here because it is referring to a specific, understood set of tax data.

Datos means data, details, or information, depending on context.

Fiscales means tax-related or fiscal.

So datos fiscales can mean:

• tax data
• tax details
• tax information

In real-life usage, it often refers to the taxpayer’s official tax information already known by the tax authorities.

Because it agrees with datos, which is plural.

• el dato fiscal = the tax detail / tax item
• los datos fiscales = the tax details / tax data

In Spanish, adjectives usually agree in gender and number with the noun they describe, so:

• dato → singular
• datos → plural
• fiscal → singular form
• fiscales → plural form

The subject is El borrador de la declaración.

The verb is incluye = includes.

So the structure is:

• El borrador de la declaración = subject
• incluye = verb
• los datos fiscales = direct object

In other words: The draft tax return includes the tax data.

Because the subject is singular: el borrador.

Even though datos fiscales is plural, that is the object, not the subject.

Compare:

• El borrador incluye... = The draft includes...
• Los borradores incluyen... = The drafts include...

So incluye matches el borrador, not los datos.

Because the personal a is mainly used with specific human direct objects, and sometimes pets or personified beings.

Here, los datos fiscales are things, not people, so no a is used.

Compare:

• Veo a María. = I see María.
• Incluye los datos fiscales. = It includes the tax data.

Yes, but the meaning changes slightly.

• incluye los datos fiscales = it includes the tax data / the specific tax information
• incluye datos fiscales = it includes tax data in general / some tax information

In this sentence, los sounds more natural because it refers to a specific set of tax details already known in the situation.

Yes, incluye comes from incluir.

It is a regular present-tense form for él/ella/usted:

• yo incluyo
• tú incluyes
• él/ella/usted incluye
• nosotros incluimos
• vosotros incluís
• ellos/ellas/ustedes incluyen

A learner might notice the y in incluyo. That is normal in the yo form of verbs ending in -uir (except some verbs like huir, which behave a bit differently in other forms too).

Yes, some changes are possible, but they may sound different in emphasis.

For example:

• El borrador de la declaración incluye los datos fiscales.
  Neutral and natural.

• Los datos fiscales están incluidos en el borrador de la declaración.
  More passive in meaning: The tax data are included in the draft return.

The original sentence is the most straightforward way to say it.

It is understandable everywhere, but it is especially natural in Spain because of the tax-administration context.

In Spain, terms like:

• borrador
• declaración
• datos fiscales

are very common in official tax language, especially when talking about la declaración de la renta.

So the grammar is general Spanish, but the phrase feels particularly familiar in Spain.

A very literal translation is:

The draft of the declaration includes the tax data.

But more natural English would usually be:

• The draft tax return includes the tax information.
• The draft return includes the tax details.

So although the Spanish uses declaración, English often prefers tax return in this context.