Repay for others, just write down what it is and why you have to repay for others. Of course, that's all, it's still not enough. If you pay for others, it's a matter of money. No matter how good the relationship is, you should know it. If you don't communicate in advance, it may bring some misunderstandings, and the relationship will be very complicated in the future. Therefore, oral communication in advance is a prerequisite and also very important.