A good tax policy should do more than just encourage behavior that is productive. It should recognize that good behaviors tend to save taxpayers money.

When people donate to charities, for instance, they willingly provide needed services to the poor, and that relieves some of the pressure on government programs. When people elect to buy their homes, going into debt to do so, they are investing in the long-term success of their communities. Homeowners tend to be responsible citizens who contribute long term and bring stability to neighborhoods. This also saves taxpayers.

A flat tax, while it may sound attractive, doesn't recognize how these private decisions offset public costs. Whether deductions for these things result in increased contributions or a spike in home ownership is of secondary concern. The relevant question has to do with fairness. People who make government's burden — which translates into the tax burdens of all other residents — light deserve a break.

State lawmakers and others who are part of an effort to overhaul Utah's tax system are beginning to talk seriously about a flat tax. Mostly, they tout its simplicity. Without a list of deductions to consider, people would have a much easier time filing their state returns each year.

But they cannot tout the plan as inherently more fair than the current system — not without answering some important questions. The first of these has to do with how income would be figured. For hourly or salaried workers, that's easy. A flat percentage tax would be required from the worker's gross yearly earnings. But what about people who rely primarily on income from investments?

A decade ago, plans for a federal flat tax suffered because they would have exempted such income from taxes all together. Many wealthy people rely on such money.

And what of businesses? Would they be required to pay?

A flat tax is inherently unfair in that a levy of, say, 5 percent would place a bigger burden proportionally on someone who earns $20,000 a year and has children than on someone who earns $100,000 and is childless. Would the plan mitigate this in any way? Again, a decade ago the plan that received the most attention in Congress would have exempted any family earning less than about $36,000 per year. Surely, any Utah plan would have to exempt the very poor at some level, taking into consideration the number of dependents.

The Church of Jesus Christ of Latter-day Saints, which owns this newspaper, has already spoken against any flat tax that would eliminate deductions for charitable contributions. Clearly, there are other behaviors and factors that deserve consideration, as well.

We applaud state leaders for examining ways to simplify the state's tax code. But we also urge them to remember that simplification must be weighed against issues of fairness and the need to reward behaviors that save the government money.