You may, for example, write a letter or email saying, "You say I owe you PS1000, but I am ready to compromise and pay you PS500." Now, unless you put "without prejudice" on this message, the opposite party might use it at a later court hearing or trial to establish that you concede owing them at least PS... Alternatively, if you want to be really formal, you can write, "I agree with your statement that... but only if there is no objection from you." This shows that you accept what they said but want to include some kind of condition attached to it. Or, if you want to be even more formal, you can write, "I agree with your statement that... but only if it does not affect any existing legal rights that my client has." In other words, "I agree with your statement if you don't try to sue me later on." These are all examples of how to use the phrase "without prejudice". It means that whatever was said in the conversation, letter, or document cannot be used as evidence against you in a court of law, because it shows that the person accepting it did so without attaching any conditions to it.