A prestação foi paga por débito direto.

Here, prestação most naturally means an instalment or a payment due as part of a series.

So A prestação foi paga por débito direto is about a payment such as:

• a loan instalment
• an insurance payment
• a monthly plan payment
• a finance agreement instalment

Be careful: prestação can mean different things in other contexts, but in financial language it very often means instalment.

A is the feminine singular definite article, meaning the.

It is used because prestação is:

• feminine
• singular
• referring to a specific instalment/payment

So:

• a prestação = the instalment / the payment
• uma prestação = an instalment / a payment

If you changed it to Uma prestação foi paga por débito direto, it would sound less specific: An instalment was paid by direct debit.

Because prestação is a feminine singular noun, and the past participle in this passive structure agrees with it.

The pattern is:

• ser
  • past participle

So:

• foi = was
• paga = paid in feminine singular form

Agreement examples:

• A prestação foi paga → feminine singular
• O valor foi pago → masculine singular
• As prestações foram pagas → feminine plural
• Os montantes foram pagos → masculine plural

This agreement is very important in Portuguese.

Yes. It is a passive voice sentence.

Active idea:

• Someone paid the instalment by direct debit.

Passive version:

• A prestação foi paga por débito direto.
• The instalment was paid by direct debit.

Structure:

• A prestação = the thing affected
• foi = was
• paga = paid
• por débito direto = by direct debit

Portuguese uses this kind of passive structure very much like English.

Here por means something like by or through, indicating the method used.

So:

• paga por débito direto = paid by direct debit

This is a natural way to talk about the means of payment.

Depending on context, Portuguese may also use expressions like:

• por transferência bancária = by bank transfer
• por multibanco
• em numerário = in cash
• com cartão = by card / with a card

So por is not always the only preposition possible in payment expressions, but in por débito direto it is perfectly natural.

Because débito direto is being used as the name of a payment method in a general sense.

So Portuguese normally says:

• por débito direto
• por transferência bancária

rather than:

• por o débito direto ✘

You may sometimes see an article in other sentence structures, for example:

• O débito direto foi ativado.
  = The direct debit was activated.

But after por, when naming the method, no article is normally used.

In European Portuguese, débito direto is direct debit: a system where a company automatically collects money from your bank account.

It is standard financial vocabulary in Portugal.

A learner should notice that this is a fixed expression:

• débito = debit
• direto = direct

Together:

• débito direto = direct debit

Yes, this is the normal term in Portugal.

A Brazilian learner would more often encounter:

• débito automático

So:

• Portugal: débito direto
• Brazil: débito automático

Both refer to the same basic idea, but the wording differs by variety.

This is a very useful distinction.

• foi paga = was paid
  Focuses on the action/event of payment.
• está paga = is paid / has been paid
  Focuses on the current result/state.

Compare:

• A prestação foi paga por débito direto ontem.
  The instalment was paid by direct debit yesterday.
  → emphasis on the event

• A prestação já está paga.
  The instalment is already paid.
  → emphasis on the fact that nothing is owed now

In many situations, both are possible, but the nuance changes.

Yes, in some contexts you could, but it is not exactly the same wording.

• A prestação foi paga por débito direto.
  Focuses on the payment method.

• A prestação foi debitada em conta.
  Focuses more on the fact that the amount was debited from the bank account.

Both can refer to a similar real-life situation, but the first is the clearer and more standard way to say paid by direct debit.

Good question. Modern standard spelling uses direto, without c.

So today you will normally see:

• débito direto

Older spelling, or more conservative spelling before orthographic changes, often had:

• débito directo

For modern learning purposes, especially in current materials, direto is the form to learn.

It would become:

• As prestações foram pagas por débito direto.

Notice all the changes:

• A → As
• prestação → prestações
• foi → foram
• paga → pagas

This shows both number agreement and gender agreement in the passive structure.

Yes. That is one reason learners sometimes get confused.

Depending on context, prestação can refer to:

• an instalment
• a benefit/payment
• part of expressions like prestação de serviços = provision of services

But in a sentence like A prestação foi paga por débito direto, the financial meaning instalment/payment due is by far the most likely one.