Hello,

You are not going to need any kind of GAP Certificate. Because you have already taken admission last year. So I don't think so It will be considered as GAP year. But you will have to choose your NEET code carefully. As it has mentioned whether your exam has been conducted or not and practicals were already included or not, it would be difficult for me to assume your code. But your code will be either 07 or 04.

I am mentioning the link of NEET article, go through this link to get detail about all the Codes and select your code accordingly,

https://www.google.com/amp/s/medicine.careers360.com/articles/neet-eligibility-criteria/amp

Good Luck.