If you are appearing for the UPSC CSE 2023, then you have to choose the appearing for the examination options. So with this option, you won't be required to submit the details if not available, you need to submit an undertaken which will be made available on the USPC CSE website. This undertaken will mention a date, before which you will be bound to submit the related documents. The time provided by UPSC for the submission of the documents is sufficient and the results comes out much before the deadline. So you have nothing to worry about.

For more information regarding UPSC CSE 2023 consider the link below:

https://competition.careers360.com/articles/upsc-ias-application-form

I hope this helps. Wish you a great day!