There are no such instructions on the official bulletin of NEET. If any where in the application, block letters are required, the system will automatically take block letter inputs.

Now if you wish you can fill the form in Capital also there is no problem with that. You must ensure that the information you are putting are correct and the spellings are correct, because many times the student makes silly mistakes in spelling of names or any other information in application form. So be careful about that.

For more information regarding NEET consider the link below:

https://medicine.careers360.com/exams/neet

I hope this helps. Wish you  a great eve!