Remember that Reader's Digest subscription you renewed last year? Chances are you owe the state about a dollar in sales tax.

Or how about those $75 hiking boots you ordered from L.L. Bean? The state wants its share: $4.69.And that $200 gold necklace you ordered from the Home Shopping Network? Better send your $12.50 to the State Tax Commission.

Not that you, or probably 99 percent of the rest of the tax-paying public, will. But people should, says Tax Commissioner Roger Tew.

"Yes, it's a legal obligation," he said. "An amount equal to the sales tax."

That legal obligation is the state's "use tax," a 6.25 percent tax imposed on all purchases made in other states but consumed in Utah. It's a tax that would put $16 million into state tax coffers, if only Utahns paid it.

Currently, the Tax Commission collects about $150,000 in use taxes owed.

"It's not a new tax," Tew said. "We've had a use tax for more than 50 years. It's just that few people pay it."

In fact, Utahns are supposed to pay the tax on all purchases made in another state (minus any sales taxes paid in the other state). That includes mail order purchases, catalog sales, telephone orders and purchases made in person.

"If you ask most Utahns if they know they are supposed to pay a use tax on magazines purchased out of state, they will say no," Tew said. "Most people know if they purchase a car out of state they have to pay the tax, but they don't when it comes to all the other purchases they make."

While most Utahns don't pay the tax, a handful dutifully enter their debt on line 18 of their individual income tax returns, even though the state never knows if money is owed or not.

"How do you enforce the law?" Tew said. "There's no way, at least not for individual taxpayers. There is a certain voluntary component of the use tax law."

But because business purchases are carefully chronicled by company books, it is much easier for the State Tax Commission to audit out-of-state purchases by businesses. As a result, the Tax Commission collects a significant amount of use tax from Utah businesses, about $29 million last year.

However, the amount collected from businesses has dropped dramatically in recent years, from $41 million in 1984 to $38 million in 1985 to the $29 million in 1986.

The amount collected from individuals rose from $105,392 in 1985 to $153,743 in 1986.

At a national level, most states are supporting a bill before Congress to require national mail-order companies with annual sales over $5 million to collect sales taxes and remit them to the state of the purchaser.

With the booming popularity of catalog sales, buying clubs and television shopping, the amount of sales tax revenue being lost totals billions of dollars annually. In Utah, the total being lost each year is conservatively estimated at $12 million to $16 million.

And the estimate doubles every seven years.

Catalog sales have indeed "gone from a small amount of purchases to a very significant amount," said state economist Doug Macdonald. And its significance in terms of tax revenue potential to the states is mushrooming.

As a result, "The revenue agencies of all states are becoming much more aggressive in their pursuit of taxes legally owed, and Utah is no different. We have to balance the budget," Macdonald said.

Macdonald and Tew agree that Utah's use tax is not so much an honesty issue as it is a fairness issue.

"When the store on Main Street that collects a sales tax has to compete with a mail-order company that doesn't, it becomes a fairness issue," Tew said.