I haven't applied for the national civil service exam yet! Is it too late to report to class after registration?

It's not too late to review yourself, but you should be prepared in advance. You should be able to register on 15. After you sign up, you should check the progress of your review, and then ask what class you need to sign up for. You can go to Henan Hangbo for consultation, and that counseling institution will recommend admission according to your personal situation.