You need to submit PPF - Form H. Download it from here -
http://www.indiapost.gov.in/pdfForms...ntinuation.pdf
Till what points we can renew the PPF account? (Means 15 years then 20 years then 25 years)
Or is there any limit?
There is no limit. This facility can be availed for period of 5 years on the expiry of 20th years and yet another 5 years on the expiry of 25 years and so on.