The section 17 of Registration Act provises leases of immovable property from year to year, or for any term exceeding one year, or reserving a yearly rent; months requires compulsory Registration.
However a lease agreement of 11 months does not require compulsory Registration.
In my view an unregistered lese argeement of 11 months is legally valid document.
For 11 month lease you don't need to go for registration but you still need to pay 2% stamp duty to make it a legal document. Just purchase stamps for that value, sign them and attach with your rent agreement.
Sir, you can even get it notrized ,if you are keeping 11 months in mind.Its is leagally valid or else go for 3 years lease & then get it registered. Keep locking period for 1 year & notice period of 3 months either side.
it is not compulsory, normally people go with a simple agreement on 100rs stamp paper, but to be on safer side it will be better to register agreement, cost can be bear by both party 50%-50%, or as per your mutual undrestanding,