If you want to keep your loan active so that you can apply for a top-up later, you need to maintain a minimum outstanding balance of Rs. 150. This small amount generates a nominal interest, which keeps the loan account active.
Why you cannot go below Rs. 150
If the balance is too low, the interest works out to a few paise and cannot be paid. That can lead to interest defaults, which affect your credit score and repayment history.
When to close instead
Once you have repaid almost the entire loan, it is better to close it rather than keep a very small balance, unless you plan to take a top-up loan in the future.
The loan tenure is 3 years, and the Rs. 150 balance cannot be carried beyond that period. After the tenure ends you must close the loan and apply for a new one if needed.