Nếu không mang tiền mặt, tôi sẽ thanh toán bằng thẻ ở cửa hàng đó.

Vietnamese often omits the subject when it is already clear from context.

In this sentence, the main clause has tôi, so listeners naturally understand the first clause as:

• Nếu (tôi) không mang tiền mặt...

So yes, Nếu tôi không mang tiền mặt is also correct. The version without tôi sounds more natural and less repetitive in many contexts.

Here mang means carry / have with you / bring along.

So không mang tiền mặt means you do not have cash on you, or you did not bring cash with you.

This is slightly different from:

• không có tiền mặt = not having cash
• không mang tiền mặt = not carrying cash with you

In this sentence, mang is a good choice because it refers to what you have on your person when going to the store.

Nếu means if.

In Vietnamese, a common pattern is:

• Nếu ..., thì ... = If ..., then ...

But thì is often optional, especially in everyday speech and writing. So these are both fine:

• Nếu không mang tiền mặt, tôi sẽ thanh toán bằng thẻ.
• Nếu không mang tiền mặt, thì tôi sẽ thanh toán bằng thẻ.

The version without thì is a little more compact and still completely natural.

Sẽ marks the action as future or expected.

So:

• tôi sẽ thanh toán = I will pay
• tôi thanh toán = I pay / I am paying / I will pay, depending on context

In this sentence, sẽ makes the result of the if clause clearly future:

• If I don’t have cash, I will pay by card.

If you remove sẽ, the sentence can still work, but it sounds a bit less explicitly future and can feel more like a general habit or plan.

Both can mean to pay, but they are used a little differently.

• trả tiền = everyday, general pay
• thanh toán = more formal or transaction-focused, often used for bills, checkouts, and payment methods

In a store context, especially when mentioning payment by card, thanh toán sounds very natural.

For example:

• Tôi trả tiền bằng thẻ. = natural, everyday
• Tôi thanh toán bằng thẻ. = also natural, a bit more formal/polished

Bằng is used to show the means or method: by, using, with the help of.

So:

• thanh toán bằng thẻ = pay by card
• viết bằng bút = write with a pen
• đi bằng xe buýt = go by bus

Using với here would not be the normal choice. Với often means with in the sense of accompaniment or relation, not method.

So for payment method, bằng thẻ is the standard phrasing.

Not necessarily.

Thẻ by itself just means card, and in context it usually refers to a bank card or payment card.

If you want to be more specific, you can say:

• thẻ tín dụng = credit card
• thẻ ghi nợ = debit card
• thẻ ngân hàng = bank card

In everyday situations, bằng thẻ is often enough if the exact type of card does not matter.

Because tiền mặt specifically means cash.

• tiền = money
• tiền mặt = cash

This matters because the sentence contrasts two payment methods:

• cash
• card

If you said only tiền, it would be less precise, because tiền could refer to money in a general sense, including money in your bank account.

In Vietnamese, place expressions often come after the main verb phrase, especially when the sentence first states the action and then the location.

So this order is natural:

• tôi sẽ thanh toán bằng thẻ ở cửa hàng đó

It means I will pay by card at that store.

Vietnamese word order is somewhat flexible, but this version sounds smooth and straightforward. Moving the location earlier is possible in some contexts, but the original order is very natural.

Đó means that.

So:

• cửa hàng đó = that store

A few useful comparisons:

• cửa hàng này = this store
• cửa hàng đó = that store
• cửa hàng kia = that store over there / that one farther away

In many everyday situations, đó is the most common neutral way to say that.

Yes, it is helpful because it separates the if clause from the main clause.

• Nếu không mang tiền mặt, tôi sẽ thanh toán bằng thẻ ở cửa hàng đó.

This makes the structure easier to read:

1. condition: Nếu không mang tiền mặt
2. result: tôi sẽ thanh toán bằng thẻ ở cửa hàng đó

In casual texting, people may leave commas out, but in standard writing, this comma is a good idea.

Yes, you could, but the meaning changes slightly.

• Nếu không mang tiền mặt = if I am not carrying cash / didn’t bring cash with me
• Nếu không có tiền mặt = if I don’t have cash

The first focuses on what you have with you. The second is broader and can simply mean you do not possess cash at that moment.

In a shopping situation, không mang tiền mặt is very natural because it suggests you came without cash and will use a card instead.