a mortgage deed form may be a legally binding document between a lender and someone buying a piece of property, such as a house. once the mortgage is paid off, the mortgage deed is then converted. a mortgage deed is a legal document that shows the transfer of real estate. information about both parties is needed for the mortgage deed. because the mortgage deed deals with major lenders and large amount of money, it is important to get legal advice about filling in the document. in the united state, a mortgage deed is commonly called a mortgage. a mortgage deed is a document that you give to the lender that creates a lien on the property.