WITH ALL THE pork that’s been stuffed into this summer’s tax giveaway legislation in the Congress, it’s easy to miss a relatively small provision that would provide a federal income tax deduction for sales taxes.

The provision, which revives a deduction that was eliminated as part of an income tax overhaul in 1986, probably won’t affect South Carolinians, because taxpayers would have to choose between deducting state income taxes or deducting sales taxes, and people who itemize tend to pay more in income taxes than in sales taxes.

But it raises important tax fairness questions that should be, but probably won’t be, considered at the federal level. And it brings to the fore an issue that needs to be considered as both the Legislature and voters in individual counties — including Richland and Lexington — consider proposals to increase the sales tax in return for lower property taxes.

On the federal level, the measure would primarily benefit people in the states that don’t levy an income tax — Texas, Washington, Florida, Nevada, Wyoming, Tennessee and South Dakota. The very reasonable idea is that folks in those states pay as much in state taxes as those who live in states that charge an income tax, yet they don’t get the same federal tax benefit as everyone else.

But while the current situation is unfair, the proposed fix would also be unfair: People in the seven sales tax states would suddenly get more of a tax break than people in the other 43 states. That’s because people in the seven sales-tax states would get to deduct pretty much all the state taxes they pay, while the rest of us, who fund our state governments with a mixture of sales and income taxes, would still deduct only about half of our state taxes.

Perhaps a partial fix is better than no fix, but as long as anyone in the country has to pay federal taxes on money they’ve already paid in state and local taxes, there’s a problem. As the Fort Lauderdale Sun-Sentinel pointed out: “The federal income tax system, originally envisioned in 1861 and later ratified by the 16th Amendment in 1913, embraced state and local tax deductions as a necessity of federalism, which promotes the idea that states should decide for themselves how to collect revenues without meddling from Washington.”

That’s where South Carolina tax policy comes into play.

Although state legislators ignore it, the fact is that federal tax policy does affect what a wise state tax policy would be: As long as we can’t deduct sales taxes, but we can deduct income and property taxes, there are serious questions as to whether it makes sense to trade a higher sales tax for lower income or property taxes.

That’s not to say it’s automatically a bad idea. My colleagues and I, for instance, have yet to come to a conclusion as to whether something along the lines of the Quinn-Sheheen tax reform plan — which increases the sales tax by 2 cents on a dollar in return for slashing property taxes — would be a good change. The loss of the federal income tax deduction is one of the arguments against the swap, but there also are arguments in favor. What is essential is that we be aware of this, and that we factor it into any decision we make.

That starts this fall, when Richland and Lexington county voters decide whether to increase the sales tax to 6 cents in return for lower property taxes. If history is any indication, the counties will run numbers that allow most people to calculate roughly how much more they would pay in sales taxes and how much less they would pay in property taxes if the measures were approved.

But there probably won’t be any numbers suggesting how much more they will pay in federal income taxes if the change is approved. Individuals will have to make that calculation themselves, working from the estimate of their property tax savings. (If you don’t itemize, then it doesn’t affect you. If you do, go to your most recent tax return, subtract that savings from your itemized deductions, then recalculate your tax bill based on the lower number.)

Of course, deciding tax policy should be about more than how it affects us personally. There are statewide economic implications to reducing property taxes. In 2001, S.C. taxpayers claimed $529 million in property tax exemptions on their federal income tax returns. That means those South Carolinians — just under a third of the taxpayers — would pay about $100 million more in federal income taxes if property taxes were replaced entirely by the sales tax. That means the Quinn-Sheheen plan, which would cut property taxes by about half, would increase federal tax liability by about $50 million, on the one hand, but bring in an additional $100 million in sales taxes from tourists.

Beyond the dollars and cents, deciding tax policy should be about creating a system that is more fair, that is more stable, that is less likely to negatively affect economic activity in a given area. And while we would probably collect more money from tourists than we would lose to the federal government, I’m not convinced that increasing the sales tax — absent significant changes in what is subject to that tax — comes out ahead on any of those points. But that’s another column.

Ms. Scoppe can be reached at cscoppe@thestate.com or at (803) 771-8571.