It's no wonder that the number of Americans calling for tax reform is growing. The reform roster includes lawmakers, economists, Treasury officials, private citizens, Democrats, Republicans - you name it.
The issue is whether the nation's highest elected officials will muster the political courage, and the persistence, needed for meaningful reform. The more than 100 basic exemptions and deductions existing in the current tax structure - often dubbed ''tax expenditures'' by economists - add up to a loss in revenue for the Treasury of over $330 billion annually. Enacting a genuine tax-reform plan will require political statesmanship.
Given the resistance to tax reform, one cannot help sympathizing with Treasury Secretary Donald Regan, who recently said he will propose an overhaul of the tax system. Mr. Regan's presumed plan? A modified flat tax that would eliminate most existing tax breaks. The plan is expected to be announced later this year.
President Reagan has called for tax simplification, and, in fact, has supported some form of flat tax to replace the existing graduated income tax. A flat tax would eliminate most deductions, credits, and exemptions; instead it would impose one ''flat'' tax rate, or only a few rates, on all taxpayers. Mr. Reagan has said he would retain the mortgage interest deduction for homeowners.
Democratic challenger Walter Mondale argues that a flat tax along the lines of the Regan plan would merely mean additional tax breaks for the wealthy - a view that he seemed to repeat in the debate last Sunday night. In that debate Mr. Mondale argued that his tax-increase proposal to reduce the federal deficit ''protects everybody from $25,000 a year or less against any tax increases and treats those $70,000 and under in a way that is more beneficial than the way the President proposes with a sales tax or a flat tax.'' Still, Mr. Reagan has not yet thrown his support behind any specific sales tax or flat-tax plan.
* Tax increases: Mondale is right in seeking additional revenues to reduce budget deficits. That is not to say that his tax package is necessarily the right step. Raising taxes at a time of economic uncertainty seems dubious. Indeed, the current recovery has to a large extent been a consumer-led recovery. Personal tax increases could adversely affect future consumer spending. But a balanced policy of budget cuts (in defense programs), coupled with modest tax-increase measures (such as a minimal surtax), might be workable.
Lawmakers could also consider adoption of a value-added tax (VAT). Under such measures, common in Europe, a tax is added to the cost of a product at each stage of the production or wholesale-retail process.
* Structural reform: Treasury chief Regan and President Reagan are on solid ground in seeking fundamental structural reform. Congress now has two major flat-tax plans before it, the Bradley-Gephardt measure (both authors are Democrats) and the Kemp-Kasten plan (both Republicans). In other words, the Republican White House is hardly alone in seeking tax simplification.
A final point: The American tax structure, for all its complexity, is really but a babe in the woods. Congress didn't get around to imposing a limited personal income tax until the Civil War. It lasted only briefly. In 1894 Congress enacted a modest income tax of 2 percent on incomes over $4,000. The Supreme Court struck down that law the next year. The present income tax was enacted back in 1913. It was hardly draconian: A married person earning $5,000 - a princely sum back then - paid about $10. And tax withholding didn't start until the 1940s.
So in that context, reform makes sense. The American tax system - still a basically ''young'' system - could use some fundamental alteration.