it’s a deal

این در اصل به معنای "من با شرایط این توافق نامه موافقم/I agree to the terms of this agreement" یا "پیشنهاد شما را می پذیرم/I accept your offer" است.
مثال؛
For instance, if someone suggests a trade or exchange, you can accept it by saying, “It’s a deal!”
When negotiating the terms of a contract, you can indicate your acceptance by saying, “If you agree to these conditions, it’s a deal. ”
If someone proposes a plan or offer and you are on board, you can confirm by saying, “I like the idea, it’s a deal!”