SALT LAKE CITY -- The amount of sales tax consumers pay in Utah would be the same regardless of the city or county where a purchase is made under a proposal being considered by legislators.

The state charges a single sales tax rate of 4.75 percent, but cities and counties can -- and do -- add taxes beyond that.

The total amount of sales tax consumers end up paying ranges from 5.75 percent to 8.1 percent. But three proposals unveiled Wednesday by Rep. Wayne Harper, R-West Jordan, would create a single sales tax rate of 6.5 percent and a fourth proposal would set it at 5.75 percent.

The problem with having sales tax rates change at city and county lines is that it makes it difficult for businesses with multiple locations to administer the tax correctly and for the state to collect what is due, Harper said.

"The closer we can get to one rate, the easier it is to administer and the less likelihood mistakes are made. We're very much in favor of simplifying it with one rate," Jim Olsen, president of the Utah Retail Merchants Association, said at an interim Taxation and Revenue Committee meeting Wednesday.

Under Harper's proposals, the loss in local option sales taxes for cities and counties would likely have to be made up by raising property taxes, he said. But it's something that needs to be considered, he said.

"What should the tax policy be for the state of Utah in conjunction with sales tax? Sales tax is a state tax and it should be imposed and managed by the state," Harper said.

But establishing a single sales tax rate won't be simple, said Bryant Howe, assistant director of the Office of Legislative Research and General Counsel.

The complex part in adjusting the sales tax for local governments is figuring out how to maintain revenues generated for transportation projects, Howe said. Local governments can charge a sales tax of one-fourth of 1 percent for those projects, which generated about $120 million in revenue statewide each of the past four years, according to statistics from the business-backed Utah Taxpayers Association.

In some of the proposals, that transportation tax would be eliminated and made up with property taxes while in others it would be continued or raised, depending on the population of the county.

"I have some heartburn with maybe doing some partial or full property tax shifts on this," Harper said. "It's become pretty apparent to me as I've been dealing with this ... there will be more states over next few years going to a unified statewide rate because of problems they're experiencing with their sales tax. We have states now above 12 percent with sales tax with most of their consumable goods."

Harper's plan comes on the heels of the state reducing its sales tax on unprepared food from 4.75 percent to 2.75 percent. Gov. Jon Huntsman and House leaders had wanted to see the tax on food completely removed -- including the local option -- but they couldn't sway Senate leaders who feared it would destabilize the tax base.