The balance of a mortgage owing on the date of death is allowed as a deduction from the value of any real property securing such mortgage. In the case of real property held by a decedent and a surviving spouse/civil union partner as tenants by the entirety, the amount of any mortgage owing on such real property at the decedent's death is not allowable as a deduction since such property is exempt from the New Jersey transfer inheritance tax.
N.J. Admin. Code § 18:26-7.4