Interest in your PPF account is calculated on the lowest balance between the close of the fifth day and the last day of every month and is credited to the account at the end of each financial year i.e., on 31st March. So if you invest by the 5th of the month, you will be eligible to interest for the full month in which you are investing.
So if I deposit on March 3rd , I will get interest only for Month of March i.e. (PPF interest)* Amount/12 . I will not get interest for the full year.
