There can be many reasons why your account is idle for some time. Job changes, transfers, relocation on foreign assignments, sickness, death, accidents etc. Now a days a new dimension is added. Most of the person now a days hold multiple bank accounts over the time. Each bank's netbanking has different login/password rules. Add to this many more login/passwords now a days that of including emails, LIC, mutual funds, subscriptions, phone accounts - only to name a few. Also some banks have two passwords, some force you to change the password in a while. The end results is that a person loses track of some of his/her bank account. May be ATM card is misplaced or password could not be recovered.
If you don't use your bank account for some period then banks label it as “inactive” account. It can happen because of no activity in your account for some time typically around 1 year. This varies from bank to bank and is not mandated by RBI. This is just to safeguard bank's customers so that no fraudulent activity takes place in one's account just because one has gone abroad to a foreign country or has been transferred to another place so lost touch with one's bank account.
Once your account is declared inactive, certain limitations are placed on the customer account - for example cheque book may not be issued. To come out of inactive accounts one needs to typically carry out ATM/cheque transaction. However rules vary and you should contact bank customer care department to know about the actual procedures.
Only recently the dormant account period was 6 months and in 2009 RBI mandated that Dormant period should now be extended to 2 years( see this rbi notification). That means in case of lack of any activity in your account from your side your account will first turn into inactive and subsequently into a dormant one. Even more restrictions apply in dormant bank account. You can do absolutely no transactions in your dormant account.
To make it active you( and all other holders) must now visit bank with all your proofs(id proof, address proof etc). Also KYC norms will be enforced, so don't forget to carry your PAN Card.
(ix) There should not be any charge for activation of inoperative account.It's clear that there is no "must" but only "should" advisory is there which is not compulsory for banks to follow.
Previously it was 6 months of inactivity that'd make your account dormant or inoperative. Currently it's different. It can change at any time. So better do one transaction every 4 months.