The NPS has two sub-accounts called the Tier I and Tier II. Tier I is compulsory while Tier II is optional. The Tier-I account is a non-withdrawable retirement account where withdrawal is allowed only if the exit conditions are met. Tier II account is optional as an add-on and subscribers can withdraw their savings from this account anytime. Only the Tier I account has tax benefits while Tier II has none. Tier II is more like a mutual fund with unlimited withdrawal facilities while Tier I has limitations.The minimum contribution for Tier-1 is Rs. 6000/- and Tier-2 is Rs. 2000/- per financial year.