You can. It’s incredibly generous of you to do that!

You’ll need to know his account number and where the payment gets sent. It might be difficult to get this information quietly though.

Usually you’d want to call the company that is servicing the loan and ask them to calculate a payoff amount as of a specific date. That way when you make your payment, all outstanding interest is paid off as well as the balance.

That company may not give you this information depending upon laws and policies. Since you’re not the person they’re contracted with for the loan.

I used to be a loan officer / underwriter, but I never dealt with student loans which have different laws governing them, so this is the best info I have to share (it’s also been 15 years since I did that work). I used to give payoff amounts all the time to other people and organizations though. People refinance their loans all the time, so it’s very common to give out that payoff calculation when the requester has the account number and name of the loan account holder.