Every year NTA release out OMR sheet along with key after the day exam completed.But this year this NTA release   out OMR sheet along with key as per your code provided in your exam on September 28th . You can find this when you go to National Testing Agency (NTA) website.

Hello Aspirant,

National Testing Agency will release the official answer key of NEET 2020 on September 28, confirmed by NTA officials. Authorities will also provide the facility to challenge the official NEET 2020 answer key by paying Rs. 1000 per questions.

You can check this article below to get all the details:

https://medicine.careers360.com/articles/neet-official-answer-key