Hey.

NDA is conducted twice in a year, once in April and other in the month of November. April session will be NDA 1 and November session will be NDA 2. You dont need to take both of them. You can choose to appear once or twice according to your preparation and your convenience. Hence though it is conducred twice in one year it is not compulsory to appear in both. Use the link below in case you need any other information

https://competition.careers360.com/exams/nda