現金で足りない分はクレジットカードで支払いますって英語でなんて言うの？

You can either make a statement about how you plan to pay the remainder of the bill. "I'll pay the rest of the bill with a Credit card?" Rest of the bill - the remainder or the balance. Or you can ask if you can pay the remainder of the bill by credit card. "May I use a credit card to pay the balance?" May I - Asking for permission to do something. Balance - the remainder of the bill.

Sometimes, with certain products, we prefer to pay part of it with cash and the other part with our credit card. If this is the case, we can use some expressions such as: 1) I will pay part of this in cash and the rest in credit. 2) Could I pay part of this product with my credit card? 3) I will pay for the rest by credit card.

Both of these answers are a good way of asking if you can use both card and cash for one transaction. Some stores will allow this and others will not. Usually it depends on the attitude of the staff serving you.

When paying with cash, but you do not have enough cash, so want to pay for the rest with credit card, then the above statement is pretty self-explanatory . 'The balance' when talking about numerical figures, is the total after a calculation is made - in this case, a deduction.

This is usually not an issue, but asking permission in USA is usually polite if you need to split a payment. Asking is useful and will get you a better response from a busy retail worker. You may ask if you can split the payment method between cash and credit. My advice is personal opinion and not a social rule at all! You can also say, "I will need to split my payment", and the worker will understand.

When you leave an amount of money that needs to be paid this can be called the 'extra' or the 'rest' When money is leftover to be paid the term used is 'remaining balance or amount' meaning it remains or still needs to be paid by credit card explains how you will be paying it

1) By formulating it as a question, you remain very polite, while achieving the same goal. Notice how you can use "card" as a substitute for "credit card" because it is contextually clear what you are talking about. 2) Again, by phrasing it as a question you remain very polite. In this case you use the word "to put" to indicate that you would like to pay for the rest with your card. "To put" can be used in various contexts and in relation to money it is a very useful term to use. Saying "the remaining amount" instead of "the rest" is likely the most gramatically sound thing to do!