PPF account holders can withdraw 50% of the balance after 6 years without getting them taxed, subject to some conditions. Shrewed investors/tax planners invest maximum amounts after 3rd year and after 6th year, go on reinvesting the withdrawn amounts in PPF and avail maximum tax benefits, again subject to some conditions. To my knowledge, if you plan well in advance, PPF is the best form of tax planning as of date.