> No voluntary instrument shall be registered by the RD unless the owner’s duplicate certificate is presented together with such instrument, except in some cases given or upon the order of the court for cause shown.

> To affect the land sold, presentation of the deed of sale and its entry in the day book must be done with the surrender of the owner’s duplicate of the certificate of title

> Where a voluntary instrument cannot be registered by reason of refusal or failure of the holder to surrender the owner’s duplicate certificate of title, the party in interest may file a petition in court to compel surrender of the same to the Register of Deeds

> However, non-production of the owner’s duplicate of the certificate of title may not invalidate a vendee’s claim of ownership where the subsequent vendees of the same lot cannot be considered in the law to be unaware of the prior sale, on account of their relationship with the 1st vendee, since the validity
of a title to a piece of property depends on the buyer’s knowledge of a prior sale.