I was just offered a 400 yuan kickback, what should I do?

Now that you have collected it, just take it.

If you feel guilty about it, then donate money. Next time we meet, just don’t accept it anymore.

However, my personal suggestion is to take it as soon as you get it. If the thing you are doing is not a normal business that violates the principles, it is normal to have some hard work, but you are stuck with others for this small hard work. If you don't do things, it's a matter of character.

Do what you should do, do your part well, and don’t do greedy things.

Don’t talk to your boss about this kind of thing in the future. Even if you don’t accept it, you can’t talk to your boss. Who knows if your boss has accepted it or not. If he accepts it and you confess to him and express your innocence with righteous words, it is tantamount to scolding him and he will be very unhappy! You have to spend this money in front of him. The more corrupt the money, the better, without violating discipline.

Of course, what I mean by being in front of him is to find a way to let him "accidentally" know that you spent the money corruptly.