Я расплачусь наличными, потому что сегодня нельзя платить картой.

Both can mean I’ll pay, but they are not identical.

• заплачу = I will pay
• расплачусь = I will settle up / pay up / pay for the purchase

In everyday situations like paying in a shop, café, or taxi, расплатиться often sounds very natural because it focuses on completing the payment for something.

So:

• Я заплачу наличными = I’ll pay in cash.
• Я расплачусь наличными = I’ll settle the bill in cash / I’ll pay in cash.

In this sentence, расплачусь suggests the speaker is at the moment of paying for something specific.

Yes, in form it looks similar, and this often confuses learners.

• расплачусь from расплатиться = I will pay / settle up
• расплачусь from расплакаться = I will burst into tears

These are two completely different verbs that happen to produce the same form in the 1st person singular future.

So context is everything:

• Я расплачусь наличными clearly means I’ll pay in cash
• Я сейчас расплачусь could mean I’m about to start crying

Russian uses the future here because the action has not happened yet.

расплатиться is a perfective verb, so its simple future form expresses a single completed future action:

• я расплачусь = I will pay / I will settle up

This is very normal in Russian when making an immediate decision about how you will pay.

Because Russian often uses the instrumental case to express the means or method by which something is done.

Here, наличными means:

• in cash
• literally something like with cash

The basic noun is наличные = cash.
In this expression it becomes instrumental plural:

• наличные → наличными

This is similar to:

• писать ручкой = to write with a pen
• ехать поездом = to go by train
• платить картой = to pay by card

So наличными and картой are both instrumental because they express the method of payment.

Because карта is not the direct object here. It is the instrument used for paying.

So Russian uses the instrumental case:

• картой = by card / with a card

Compare:

• Я держу карту = I’m holding the card.
  Here карту is the direct object, so it is accusative.
• Я плачу картой = I’m paying by card.
  Here картой shows the means, so it is instrumental.

Both can be possible in some contexts, but they emphasize slightly different things.

• нельзя платить картой = it is not allowed to pay by card / one cannot pay by card
• нельзя заплатить картой = it is impossible to pay by card in this instance / you can’t manage to pay by card

With нельзя, the imperfective often describes a general rule, restriction, or usual possibility.
So here платить sounds very natural because it means paying by card is not allowed/possible today.

In a shop notice or practical situation, this wording is very common.

нельзя is an impersonal word meaning:

• it is impossible
• it is not allowed
• you can’t
• one must not

The exact meaning depends on context.

In this sentence, сегодня нельзя платить картой most likely means:

• paying by card is not possible today, or
• card payment is unavailable today

For example, maybe the card terminal is broken, the internet is down, or there is some temporary restriction.

Because this is an impersonal construction. Russian often expresses general possibility or prohibition without naming a subject.

So:

• нельзя платить картой = one cannot pay by card / you can’t pay by card

There is no explicit someone doing the action. It is a general statement about the situation.

This is very common in Russian:

• Здесь нельзя курить = You can’t smoke here.
• Нельзя входить = No entry / You must not enter.
• Сегодня нельзя платить картой = Today you can’t pay by card.

Yes, very often.

Russian verb endings usually make the subject clear, so you could say:

• Расплачусь наличными, потому что сегодня нельзя платить картой.

This still clearly means I’ll pay in cash... because расплачусь already shows I.

However, Я may be included for emphasis, clarity, or natural conversational rhythm. In this sentence, keeping Я is completely normal.

потому что means because and is the standard neutral way to introduce a reason.

So:

• Я расплачусь наличными, потому что сегодня нельзя платить картой. = I’ll pay in cash because today you can’t pay by card.

A shorter, more conversational alternative is так как in some contexts, but потому что is usually the most direct equivalent of because.

Word order can also change:

• Потому что сегодня нельзя платить картой, я расплачусь наличными.

This is grammatical, but the original version sounds more natural in many everyday situations.

сегодня means today and modifies the second clause:

• сегодня нельзя платить картой = today it is not possible/allowed to pay by card

Its placement is natural because it highlights that this is a temporary situation. The problem is not necessarily permanent; it applies today.

You could also hear:

• Сегодня картой платить нельзя.

This word order gives a slightly different emphasis but means the same thing.

Not in this sentence.

• наличные is the basic dictionary form meaning cash
• наличными is the instrumental form needed after this verb to express in cash

So:

• Я расплачусь наличными = correct
• Я расплачусь наличные = incorrect

You may also hear:

• оплата наличными = payment in cash
• только наличные = cash only

In только наличные, the dictionary form is used because it is not functioning the same way grammatically.

Yes, it is very natural.

Common expressions include:

• платить картой = to pay by card
• оплатить картой = to pay for something by card
• расплатиться картой = to settle up by card

You may also hear:

• по карте in some expressions, but for straightforward everyday speech, платить картой is one of the most common and natural options.

So in this sentence, картой is exactly what a learner should expect.

The main stresses are:

• я расплачУсь
• налИчными
• потомУ что
• сегОдня
• нельзЯ
• платИть
• кАртой

Stress matters in Russian, so it is worth learning these together with the words.

A natural rhythm would be something like:

• Я расплачУсь налИчными, потому что сегОдня нельзЯ платИть кАртой.