La deducción fiscal reduce el resultado de la declaración.

In Spanish, it is very common to use the definite article where English might not.

Here:

• la deducción fiscal = the tax deduction
• la declaración = the tax return / the declaration

Spanish often prefers the article when talking about a concept, category, or specific item understood from context. So even if English might say Tax deductions reduce the result of a tax return, Spanish naturally uses la in this kind of general statement.

Also, both nouns are feminine singular:

• deducción → feminine
• declaración → feminine

So the article is la in both cases.

In Spanish, adjectives usually come after the noun, unlike in English.

So:

• deducción fiscal = tax deduction
• literally: deduction fiscal

This is the normal word order in Spanish:

• casa grande = big house
• reforma laboral = labour reform
• deducción fiscal = tax deduction

Putting fiscal before the noun would sound unusual here.

Here, fiscal means related to taxes.

It does not mean fiscal in the English sense of budgetary policy only. In Spanish, fiscal is very commonly used for tax matters:

• política fiscal = fiscal policy
• delito fiscal = tax crime
• deducción fiscal = tax deduction

So in this sentence, fiscal is best understood as tax-related.

Reduce is the third-person singular present tense of reducir.

The subject is la deducción fiscal, which is singular, so the verb must also be singular:

• la deducción fiscal reduce = the tax deduction reduces

Compare:

• la deducción reduce = the deduction reduces
• las deducciones reducen = the deductions reduce

So:

• reducir = infinitive, to reduce
• reduce = reduces
• reducen = reduce for they

Because it is the thing that performs the action of the verb reduce.

Structure:

• La deducción fiscal = subject
• reduce = verb
• el resultado de la declaración = direct object

So the sentence is literally:

• The tax deduction
  • reduces
    • the result of the tax return

A good test is to ask: What reduces the result? Answer: La deducción fiscal.

Because the gender of resultado depends on resultado, not on de la declaración.

Break it down:

• el resultado = the result
• de la declaración = of the declaration / of the tax return

The phrase de la declaración only adds extra information. It does not change the gender of resultado.

So:

• resultado is masculine → el resultado
• declaración is feminine → la declaración

It means of the tax return or of the declaration, and it specifies which result we are talking about.

So:

• el resultado = the result
• el resultado de la declaración = the result of the tax return

The preposition de often shows possession, relation, or connection:

• el final de la película = the end of the film
• el nombre del hotel = the name of the hotel
• el resultado de la declaración = the result of the tax return

In tax language, this refers to the outcome of the return, for example whether you owe money or are due a refund.

Because del = de + el, and you only use del before a masculine singular noun with el.

Examples:

• de + el resultado → del resultado
• de + la declaración → stays de la declaración

Since declaración is feminine, it uses la, so you say:

• de la declaración

not del declaración.

Yes, in this context it very likely refers to a tax return.

The word declaración can mean many kinds of declaration in Spanish, but with tax vocabulary like:

• deducción fiscal
• resultado
• declaración

the meaning is almost certainly:

• declaración de la renta
• or more generally, a tax return

Spanish often omits words that are obvious from context. So instead of saying the full declaración de la renta, the sentence just says la declaración.

Yes, but in tax language it has a slightly more specific feel.

In everyday English, result can sound a little broad. In this context, el resultado de la declaración refers to the final outcome of the tax return, such as:

• how much tax is due
• whether the amount goes down
• whether you get a refund or have to pay

So while resultado does mean result, in this sentence it refers to the financial outcome of the return.

In standard Spain Spanish, deducción is pronounced roughly like:

• de-duk-THYON in much of Spain

Key points:

• -cción is a very common ending
• the cc here sounds like k + th in Spain, because the second c is before i/ón-related spelling
• ción is stressed on the last syllable because of the written accent: -ción

Very roughly:

• de-duk-THYON (Spain)
• in much of Latin America, more like de-duk-SYON

The written accent in deducción shows where the stress goes.

Because el resultado is a direct object, but it is not a person.

Spanish uses the personal a mainly before specific people, and sometimes animals or personified things:

• Veo a María = I see María
• Conozco al profesor = I know the teacher

But here:

• reduce el resultado

there is no a because resultado is a thing, not a person.

Yes. That would mean Tax deductions reduce... in a more general plural sense.

Compare:

• La deducción fiscal reduce el resultado de la declaración.
  = The tax deduction reduces the result of the tax return.

• Las deducciones fiscales reducen el resultado de la declaración.
  = Tax deductions reduce the result of the tax return.

The original sentence uses the singular, which can sound like it is talking about the concept of a tax deduction, or about a particular deduction in context. The plural version talks about deductions more generally.