Hello aspirant,

You haven't mentioned the exam that you are talking about. For instance, there are a number of competitive exams scheduled in the upcoming months so Would not be able to mention something specific.
In case you haven't got the registration number, you can try any of the following steps:

• Check your registered e-Mail or Mobile number for messages regarding your exam application.
• Visit their official site and try logging in with you ID and password.
• In case you have downloaded the application form, check it for registration number printed in the top left or right corners.

Hope this helps you.