1, Firstly registering a tenancy agreement is not the liability of the tenant but of the landlord
2. Even if you do not have a registered tenancy agreement, the rent receipt standing in your name and the possession of the tenanted premises, would suffice
3. so no need of a registered tenancy agreement in your name
5. once the landlord recognises you as his lawful tenant, then even if there is no registered document, it does not matter. its the landlord responsibility to execute and register tenancy agreement with tenant and NOT of the tenant
6. the seller tenant is having fear since she must have received consideration from you in the FY 2015-16 and already reported that receipt to the income tax
7. but the position for her wont change since the registration date relates back to the agreement execution date i.e. even if the agreement is registered later, it will relate back to the actual agreement date
8. after a document is signed, it has to be registered within a maximum period of 4 months plus additional 4 months
9. in your case that period is crossed.
10. the penalty will therefore be 2% of the stamp duty counted from the date of signing i.e Nov 2016 subject to maximum of 4 times of duty payable
11. so i suggest that instead of paying such high penalty alongwith the unpaid stamp duty, you stay put with your rent receipt and possession. thats a good title as well since registering agreement is not your liability, unless if certain utility providing companies like BEST etc insist for a registered document. but that can be taken care of as well (get the hint)