A taxa de emissão aparece no boleto.

In Portuguese, it is very common to use the definite article with nouns when talking about a specific thing or a general item that is understood from context.

So a taxa means the fee/charge.
In this sentence, it sounds natural because the speaker is referring to a particular fee that is part of the bill or payment document.

Leaving out the article and saying Taxa de emissão aparece no boleto would sound unnatural in normal Portuguese.

This is a noun phrase:

• taxa = fee, rate, charge
• de = of
• emissão = issuance, emission, issuing

So grammatically, taxa de emissão is literally something like issuance fee or fee of issuance.

Portuguese often uses noun + de + noun where English may prefer a compound noun:

• taxa de emissão = issuance fee
• cartão de crédito = credit card
• máquina de lavar = washing machine

Portuguese usually links nouns with de when one noun describes another.

English often puts one noun directly before another:

• issuance fee
• credit card
• train station

But Portuguese usually prefers:

• taxa de emissão
• cartão de crédito
• estação de trem / estação de comboio depending on the variety

So de is the normal connector here. You generally cannot just put the two nouns side by side and say taxa emissão.

Aparece is the 3rd person singular present tense of aparecer.

Here is the logic:

• subject: a taxa = singular
• verb: aparece = it appears / shows up

So the verb matches the singular subject.

A few present-tense forms of aparecer are:

• eu apareço
• você/ele/ela aparece
• nós aparecemos
• eles/elas aparecem

Yes, aparecer literally means to appear or to show up, but in practical usage it can also mean something like is shown or is displayed.

In this sentence, aparece no boleto suggests that the fee shows up on the bill/document.

This is a very natural way to say that some information is visible or listed somewhere.

Depending on context, Portuguese might also use verbs like:

• consta no boleto = is listed on the bill
• vem no boleto = comes on the bill
• está no boleto = is on the bill

But aparece sounds natural when talking about something that shows up visibly.

No is a contraction of:

• em = in, on, at
• o = the

So:

• em + o = no

That means no boleto literally means in/on the boleto.

Other common contractions are:

• na = em + a
• nos = em + os
• nas = em + as

Examples:

• na conta = in/on the account
• nos documentos = in the documents

Because boleto is a masculine noun in Portuguese.

So it takes:

• o boleto
• no boleto = em + o

If the noun were feminine, you would use na instead.

For example:

• a conta
• na conta

In Brazil, boleto usually refers to a payment slip, bank payment document, or bill that you can use to pay a charge.

It is short for boleto bancário in many contexts.

This is a specifically Brazilian term and system, so translating it simply as bill or invoice is sometimes only approximate. Depending on context, payment slip is often the most precise explanation.

Portuguese often leaves out subject pronouns when the subject is already stated or clear.

Here, the subject is explicitly present:

• A taxa de emissão = the subject

So there is no need to add ela.

Portuguese does this all the time:

• O produto chegou.
• A conta venceu.
• A taxa aparece no boleto.

Using ela here would usually be unnecessary and could sound a bit repetitive unless you wanted special emphasis.

Yes, but the original order is the most neutral and natural:

• A taxa de emissão aparece no boleto.

You could also say:

• No boleto, aparece a taxa de emissão.

That version puts more focus on where it appears, but it sounds less neutral and may feel more like spoken emphasis or stylistic rearrangement.

For a learner, the standard subject + verb + location order is the safest choice.

The stress is on the last syllable: emis-SÃO.

A rough pronunciation guide:

• emissão ≈ eh-mee-SOWN

A few useful notes:

• the ss sounds like an English s in see
• ão is a nasal sound, very common in Portuguese
• the written accent ã/ão helps show that nasal quality and stress pattern

So the most important part to notice is the ending -são, which is both stressed and nasal.

Yes, you could, and it would still make sense.

The difference is mainly nuance:

• aparece no boleto = it appears / shows up / is shown on the bill
• está no boleto = it is on the bill

Aparece focuses a bit more on visibility or the fact that it shows up there.
Está is more neutral and just states location/presence.

Both are possible, but aparece is very natural if you are talking about information that is displayed or listed.

You would make both the noun phrase and the verb plural:

• As taxas de emissão aparecem no boleto.

Changes:

• A → As
• taxa → taxas
• aparece → aparecem

This is a good example of agreement in Portuguese: the article, noun, and verb all have to match the subject.