Hi there. 

The eligibility criteria for writing the NEET examinations says that a general category candidate needs to have a score of 50% in Class XII boards examinations with the subjects of Physics, Chemistry, and Biology. 

Hence, if you are in Class XII right now you can surely apply for the NEET exam the same year as your Class XII boards. 

There's no need of substitution if you apply the same year as boards. There's isn't any option of substitution anyway because if you don't fulfil the eligibility criteria you wouldn't get to write the exam anyway. 

Wishing you luck!

Hello Anshita,
Candidates who will be appearing for the Class 12 exam in 2019 are also eligible to apply for the NEET exam. Candidates are required to fill Class 10 and Class 12 details but those who are appearing for Class 12th exam in 2019 will have to choose the “Appearing” and “Result awaited” options.
The application form for the NEET 2019 exam will release on November 1, 2018. The last date for filling up the application form is November 30, 2018.
So, dont worry. You are eligible to apply for the exam. Stay updated with the commencement of application process.
Good Luck!