NIOS students can appear for improvement exams only once for a subject during the admission period.
Other board students who have passed at least one subject may get NIOS admission under TOC to transfer their marks from their marks from other board to NIOS. Then they will to appear for NIOS exams.
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you can give the improvement exam only once and you can give the exam after passing the board exam. a candidate need to attempt the improvement exam with in five years of admission. as you have passed 12 in 2016. and you enrolled for the course in 2014. so technically 5 years have passed from 2014-2019. its not possible to give improvement exam now. follow the below link to know in details,
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