647. Effect of payment of mortgage in general.

When money secured by the mortgage has been discharged, a mortgage, other than a registered charge1, becomes a satisfied term and ceases unless the money was paid by a person having a limited interest in the equity of redemption who requires the mortgage to be kept alive by transfer or otherwise2. Hence there is no need for a reconveyance of freeholds or reassignment of leaseholds; and, although a surrender of the mortgage term is appropriate where a mortgage is discharged as to part only of the property comprised in it3, where it is completely discharged a surrender has no