designed to get taxpayers through a particularly difficult period — such as the expiring extender dealing with mortgage forgiveness. Enacted at the end of 2007 in response to turmoil in the housing market, this provision was designed to help borrowers who were underwater with their home mortgages: previously, if a lender foreclosed on a home and sold it for less than the outstanding indebtedness, the forgiveness of the unpaid balance generated taxable income for the borrower, as did a renegotiated mortgage that reduced the outstanding indebtedness. Under this temporary provision, that forgiveness is not considered income —a welcome result for taxpayers in this unhappy situation. Yet what about temporary provisions that promote favored tax policies but that don’t respond to a particular situation? If they're such a good idea, why not make them permanent? This gets to a basic reality: permanent provisions are more costly than temporary ones. That is because the Joint Committee on Taxation must use a current law “baseline” when it estimates the revenue impact of tax legislation. Such a baseline assumes that a temporary measure, such as the mortgage forgiveness mentioned above, generates only a short-term revenue loss, and will expire as scheduled — even if that is unlikely to occur. This means that such measures can paint a rosier fiscal picture than is perhaps justified, and can therefore be a more “cost-effective” way to continue desired tax benefits (and policies), regardless of how inefficient and counter-productive the resulting uncertainty may be. These current expiring extenders seem likely to languish — at least for a bit, especially considering that the House has already recessed for the year. Although Congress has often renewed expiring provisions retroactively, such a move early next year could take some of the steam out of tax reform (assuming it has a chance). In addition, despite how inherently worthy these expiring provisions may be, Congress is under le