Except if the money they are using to pay the interest and the money received from the sale of those assets is taxed appropriately. Interest on business loans should not be deductible, nor should investment losses. The government is not responsible for their poor business decisions. Of course, there can be delineations for investment loss write-offs based on total gross income from all sources. A small business owner or an individual that holds an investment account with an AGI under $1million or so would reasonably still have access to such write-offs or deductions, but anything over that $1million per year is free game, losses or not.