Hi,

As you have mentioned, you want to write the improvement examination as you got failed in several subjects in class 12th. You can do the following:

• If you are from CBSE or some board that offers improvement examination, you can fill the form, which comes after the declaration of the result. You can fill only those subjects in which you are failed. You also do no need to attempt any other subjects or practicals, the marks will be forwarded from previous result. Please ensure you apply for the improvement exam in continuation of the year of class 12th result, as no year gap is entertained and you might need to re-appear whole class 11and class 12again.
• If you are from boards like West Bengal board or similar, which do not offer any improvement examination. You need to re-attempt your class 12th again as a fresh . You chose board of your choice, (not mandatory to chose previous one).  The latest class 12th result will be considered. You might need to take admission from class 11 from certain school.

All the best.