Eliminating tax deductions for non-investment personal interest expenses (e.g., on mortgages), with reductions in personal tax rates that are both budget neutral and keep the burden of taxes by income group the same, would lead to more efficient financing decisions by individuals.
Reducing the deductibility of interest expenses for non-financial businesses to equalize the overall tax cost of debt and equity financing, while using the extra revenue to reduce personal and corporate tax rates in a budget neutral fashion that also keeps the burden of taxes the same, would lead to more efficient financing decisions by firms.
