Each week, the anticipated surplus in state tax revenue gets bigger - it's now, at a conservative estimate, over $100 million - and the debate about what to do with the money is growing.

Most business leaders, and many others as well, want the surplus to be refunded to the taxpayers. They say it would give the local economy a significant shot in arm. That is a persuasive argument.Based on the final figures compiled in the next week, the surplus could result in a 13-to-15 percent rebate to Utahns on the state income tax they paid this past year.

Most of that money probably would be spent on consumer purchases, effectively pumping $70 million to $100 million into the state economy. The multiplier effect of such money being spent by many different persons would be large indeed.

A special session of the Legislature will be held June 15 to decide what to do with the surplus. Given many of the budget problems the state has faced in recent years, there is an understandable clamor by some that it be spent for urgent needs.

But because much of the surplus is a one-time windfall arising from changes in the 1986 federal tax law, the money can't simply be spent to bolster continuing programs or give salary raises. That would only create the same need the next year when no windfall is available.

Educators want at least some of the funds to be used for school textbooks, laboratory equipment, computers, and other supplies that are in short supply. Some argue that surplus money could be put into school district trust funds, allowing the districts to use the interest earnings for local programs.

Such suggestions have merit, but the state is honor-bound to return the income tax surplus. In supporting the $160 million tax increase in 1987, the governor and Legislature promised that any surplus would be given back to the taxpayers.

At the time of the 1987 tax hike, lawmakers were aware that federal tax reform would result in an income tax windfall. But there was no way at the time to know how much - whether a great deal or very little. Such uncertainty could not be included in the record tax hike that year, so state taxes were raised and the decision on what to do with any surplus was put off until reasonably firm figures were available.

The Legislature passed a law in the 1988 session that would automatically return any income tax surplus this year by allowing a tax credit on next year's state tax forms. But giving the money back now as spendable cash would provide an immediate boost to the state's economy. Moreover, the administrative costs are such that it would cost more to give the money back as a tax credit than as a rebate.

However, there may be a way to satisfy both sides. In addition to the income tax windfall, an improved business climate has produced a sales tax surplus that may reach $20 million to $30 million.

It would appear to make sense to refund the $70 million or more of income tax surplus and use the sales tax surplus to finance other critical needs. Some of the sales tax also could be put into a rainy day fund. Despite this year's windfall, the budget crisis is not over.