IT’S NO WONDER that the sales tax always leaps to lawmakers’ minds when they start looking for an alternative to the property tax. There are only two places they can get the kind of money they need to replace property taxes in one fell swoop — the sales and income taxes. Since we pay the sales tax in relatively small amounts, most people prefer it to the property tax and even the usually invisible income tax.

And it’s encouraging that this year’s batch of property tax slashers are talking about replacing property tax revenue with some other tax, rather than simply forcing local governments to slash taxes, or even promising to make up the money with natural “growth” in state tax collections.

But before senators and representatives wade too deeply into the swap-the-property-tax-for-a-higher-sales-tax-stream (river?), it’s important to take a sober look at the current and future problems with such an exchange.

Assuming they can come up with a plan that doesn’t strip city and county councils of their taxing authority, such a switch can be made responsibly — but only if legislators make politically difficult changes to the sales tax.

There are at least three problems with our sales tax: It is deeply regressive; it is a tax that can be increased only so much before the increases drive down spending, making any increase counterproductive; and it is a tax whose base is rapidly eroding.

Fortunately, legislators can take three steps to mitigate those problems, and use the sales tax to reduce the property tax burden:

• First, exempt groceries from taxation.

Everybody has to eat; the less money you make, the larger portion of it you spend on food. So taxing groceries is the biggest reason the sales tax is regressive; and eliminating that tax is the single biggest way to make the sales tax less so.

• Next, eliminate some of the more than 60 special exemptions to the sales tax.

Clearly, some of these exemptions are justified.

We exempt many raw materials, from farm machinery to manufacturing equipment, so we won’t tax the same thing twice. Home electricity looks like a juicy target for elimination until you think about how much more regressive the sales tax would be if we did away with that one.

But just as clearly, some exemptions are not justified.

There is probably no more outrageous, unjustifiable exemption than the $300 sales tax cap on cars and trucks, which results in people paying a lower tax rate as the cost of their car increases.

Taken together, these 60 exemptions mean that for every $2 worth of products that are taxed by the state, $1 worth of products are sold without tax.

Removing some exemptions would allow us to keep any sales tax increase small enough that it won’t deter spending. Removing the right exemptions would make the sales tax a little less regressive.

• Finally, tax more services.

This is absolutely essential to stabilizing the sales tax base.

It also can help us raise more money without having to raise the tax rate too high, and help make the sales tax less regressive.

And it is the least-understood solution, because it solves the least-understood problem.

A few numbers explain things: In 1979, U.S. consumers paid state and local sales taxes on 51 percent of their consumer spending. By 2000, the portion had dropped to 42 percent. And that number is only getting lower.

The shift has occurred because of the proliferation of state sales tax exemptions, the Internet, and our move from a product economy to a service economy.

The Congress won’t let us do much about all the untaxed goods being sold over the Internet. But states are perfectly free to tax services. And they have an obligation to do so.

This isn’t as radical an idea as legislators seem to think.

According to the Federation of Tax Administrators, South Carolina already taxes 32 of the 164 categories of services, from cell phone and diaper services to auto rentals and sign installation.

In theory, if we taxed all services, we could more than double our sales tax collections. But we shouldn’t do that, for two reasons.

First, in some cases this would result in pyramiding, or double-taxation. Say we tax both legal services and accounting services. When I pay my lawyer’s bill, I would pay a tax on the total bill. But if my lawyer purchased accounting services as part of her representation, she would have already paid a tax on those services, which would be included in my bill. So I would end up paying a tax on a tax.

The other reason we shouldn’t tax all services is more significant: It would cause many South Carolinians — and particularly businesses — to take their business out of state, to avoid the tax. This probably wouldn’t affect dry cleaning businesses or delivery services, but it could determine where your accountant lives.

The key, then, is to identify the services that people need to purchase locally, and to tax them.

That’s not something legislators are lining up to do, because the people who got on the list of services that aren’t taxed (like those on the list of untaxed goods) are determined to keep their exemptions. But it’s something just about every state has managed to do to a greater extent than we have. And if legislators want to significantly reduce the property tax without increasing literally scores of other taxes and fees, it’s something they must do.

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