On the maturity of the Post Office RD account, the maturity amount i.e. the investment and interest amount will be credited to your savings account. Alternatively, you can choose to extend the maturity period by another maximum period of 5 years. In such a case you need not make any fresh deposit. You can retain the initial amount in the RD account. However, the original interest rate will be applicable. Further, you need to file an application in Form-3 to the Post Office of India. You can file it either online or by visiting the nearest branch of the Post office