A declaração do Imposto de Renda inclui o rendimento tributável.

Because in Portuguese, de + o normally contracts to do.

So:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

Here, o Imposto de Renda is a masculine singular noun phrase, so de o Imposto de Renda becomes do Imposto de Renda.

In standard Portuguese, common nouns are usually not capitalized the way they often are in English titles or official expressions.

So in normal running text, you usually write:

• imposto de renda
• rendimento tributável

You may sometimes see Imposto de Renda capitalized in official, legal, bureaucratic, or stylistic contexts, but it is not required the way a proper name would be.

A learner should know that Portuguese generally uses fewer capital letters than English.

Literally, declaração does mean declaration or statement, but in this context it refers to a tax return or tax filing.

So A declaração do Imposto de Renda means something like:

• The income tax return
• The income tax declaration/filing

This is a good example where the most natural English translation may differ from the most literal one.

Because nouns in Portuguese have grammatical gender.

• declaração is feminine → a declaração
• rendimento is masculine → o rendimento

The articles have to match the gender of the noun:

• a for feminine singular
• o for masculine singular

This is grammatical gender, not biological gender.

Because the subject is singular: A declaração do Imposto de Renda.

The main noun of the subject is declaração, which is singular, so the verb must also be singular:

• A declaração ... inclui = The return ... includes

It would be incluem only if the subject were plural:

• As declarações do Imposto de Renda incluem ...

The structure is:

• A declaração do Imposto de Renda = subject
• inclui = verb
• o rendimento tributável = direct object

So the pattern is:

Subject + Verb + Object

This is very similar to normal English word order.

Here, yes, rendimento refers to income/earnings.

In tax language, rendimento often means money received, such as salary, interest, or other earnings. Depending on context, Portuguese may also use renda, but rendimento is very common in tax and financial language.

So rendimento tributável means:

• taxable income
• literally, income that can be taxed

In Portuguese, adjectives often come after the noun.

So:

• rendimento tributável = taxable income
• literally: income taxable

This is one of the most common word-order differences from English.

That said, adjective placement in Portuguese can vary, and sometimes changing the position changes the tone or meaning. But here, the normal and expected order is noun + adjective.

Tributável means taxable.

It comes from the idea of being subject to tributo or taxation. The ending -ável often works like English -able:

• lavar → lavável = washable
• tributar → tributável = taxable

So tributável means able to be taxed or subject to tax.

Portuguese uses definite articles more often than English does.

So it is very natural to say:

• A declaração do Imposto de Renda inclui o rendimento tributável.

In English, you might sometimes omit the in similar contexts, but Portuguese often keeps the article.

Could they be omitted? Sometimes in headlines, notes, bullet points, or very technical listing style, yes. But in a full normal sentence, the articles sound natural and expected.

Yes. In Brazil, Imposto de Renda is the standard expression for income tax.

You will also often see abbreviations such as:

• IR = Imposto de Renda
• IRPF = Imposto de Renda Pessoa Física

So this is an important chunk to learn as a set phrase.

You may encounter both, but they are not always used in exactly the same way.

• declaração do Imposto de Renda often sounds like the income tax return
• declaração de Imposto de Renda can also be used and may feel more like income tax declaration/return as a type of document

In real Brazilian usage, both patterns can appear depending on style and context. For a learner, the important thing is that do here is perfectly natural and idiomatic.

A more natural English version would often be:

• The income tax return includes taxable income.

A more literal version is:

• The declaration of income tax includes the taxable income.

The Portuguese sentence is perfectly normal, but the best English translation depends on whether you want natural English or a word-for-word match.

In Brazilian Portuguese, inclui is pronounced roughly like een-KLOO-ee.

A few helpful notes:

• in- often sounds like een
• clu sounds like kloo
• -i is a separate vowel sound at the end

So you should hear inclui as three syllables: in-clu-i.

It is singular grammatically, and it can refer to taxable income as a category or amount.

Portuguese often uses a singular noun to talk about something general or abstract:

• o rendimento tributável = taxable income in a general sense

If you were talking about multiple taxable income items, then you might use the plural:

• os rendimentos tributáveis

So here the singular is normal and does not necessarily mean only one payment or one source.