Rev. Rul. 55-578

For documentary stamp tax purposes, a conveyance by a mortgagor of his entire interest in mortgaged real estate to the mortgagee, who becomes the owner of the fee simple title, removes or extinguishes the lien of the mortgage held by the mortgagee. It is immaterial that the conveyance is made to the mortgagee by an assignee of the mortgagor who has not assumed liability for the outstanding indebtedness to the mortgagee. Therefore, the unpaid balance on the mortgage cannot be excluded in the computation of the documentary stamp tax imposed by section 3482 of the Internal Revenue Code of 1939