unregistered sale deed

It can  be useful for collateral purpose of possession only.

It is invalid and inadmissible.  But can be used for collateral purposes.

1. A document required to be registered, if unregistered is not admissible into evidence under Section 49 of the Registration Act.
2. Such unregistered document can however be used as an evidence of collateral purpose as provided in the proviso to Section 49 of the Registration Act.
3. A collateral transaction must be independent of, or divisible from, the transaction to effect which the law required registration.
4. A collateral transaction must be a transaction not itself required to be effected by a registered document, that is, a transaction creating, etc. any right, title or interest inimmovable property of the value of one hundred rupees and upwards.
5. If a document is inadmissible in evidence for want of registration, none of its terms can be admitted in evidence and that to use a document for the purpose of proving an important clause would not be using it as a collateral purpose.
6. A document required to be registered, if unregistered, can be admitted in evidence as evidence of a contract in a suit for specific performance.

See,
1. CIVIL APPEAL NO. 3192 OF 2010 (SC), S. Kaladevi v. V.R. Somasundaram & Ors. (Decided o 12/04/2010)
2. K.B. Saha and Sons Private Limited v. Development Consultant Limited (2008) 8 SCC 564
3. Kalavakurti Venkata Subbaiah v. Bala Gurappagari Guruvi Reddy (1999) 7 SCC 114

In addition to Mr. Krishnna Unregistered sale deed  Can be impounded under S.33 of Stamp Act and admitted in evidence under S.37 of the Stamp Act as a contract 

Your question itself speaks about a suit for permanent injunction. It shows that you are not in possession.  Under these circumstances this unregistered sale deed cannot be accepted as an evidence but if you have anything additional documents to prove the execution of the sale deed and the reasons for non registration, then this document can be taken as a collateral evidence to show that sale consideration has passed on and the registration has been delayed due to the Vendor's fault.

As referred to by Dr. V.N.Tripathi, there are several cases for accepting this for collateral purposes only to prove the point in the particular case and not to prove the sale.

Is it possible to register the unregistered sale deed (that was done on Rs. 10 stamp paper in 1988)? What is the process in this case? (In case it differs from state to state, I am referring to Pune, Maharashtra). Also, what are the chrages here?