Taxpayers struggling with their newly unfamiliar tax forms may feel like tucking a poison-pen letter into the envelope they mail to the Internal Revenue Service, but their ire is misplaced. It is Congress, that bastion of political imperative and compromise, that deserves the blame and credit for the Tax Reform Act of 1986.

If the new law seems complex -- many taxpayers will find it simpler -- it is because democracy produces complex results. Like the tax code it replaced, the new system is the child of a hundred hard-fought battles between lawmakers with competing political philosophies and diverse constituent interests. There is far more to tax reform than forms.

"The tax code, once you get to know it, embodies all the essence of life: greed, politics, power, goodness, charity," former IRS Commissioner Sheldon S. Cohen is quoted as saying in the recent book, "Showdown at Gucci Gulch: Lawmakers, Lobbyists and the Unlikely Triumph of Tax Reform." "Everything's in there. That's why it's hard to get a simplified tax code. Life just isn't simple."

Lawmakers crafting the legislation that eventually became the 1986 tax code had to reconcile three conflicting forces: politics, fairness to lower-income taxpayers and fiscal responsibility. The convergence of those factors shaped such commonly used deductions as Individual Retirement Accounts, home-equity loans and state and local taxes -- in ways that complicated the tax forms for those deductions.

Politics required that tax breaks only be limited, not wiped out entirely. For reasons of fairness, what remained of the breaks was targeted to lower- and middle-income taxpayers. And the need to hold down the federal deficit decreed that each time a legislator proposed restoring a tax break, thus reducing revenue collections, he also had to propose a commensurate tax increase.

"I don't know how you say it politely, but the political process requires a certain amount of lubrication," said Tom Persky, former legislative liaison for the IRS. Political and economic compromises provided the grease that smoothed the tax bill's passage.

The early tax-revision proposals by the Treasury Department and by Rep. Richard A. Gephardt (D-Mo.) and Sen. Bill Bradley (D-N.J.) actually would have simplified the tax code, by wiping out a host of deductions and credits while reducing tax rates.

The idea was a grand one: to take the tax code out of financial decisions, to remove the unproductive loopholes that made the economy less efficient and to encourage people to work and save more by reducing their tax rates.

Bradley and Gephardt contended that their plan would make the system so simple that taxpayers could file their returns on a small postcard.

But that was before politics entered the picture. As President Reagan and Congress began crafting their versions of tax revision, the mounting pressures added complexity by the bucket load.

Take the fate of Individual Retirement Accounts, which like other widely used deductions were the object of heated debate during the two years that Congress considered tax revision.

Under the old law, IRAs allowed any taxpayer to deposit up to $2,000 per year in a special account designated for use after retirement, and deduct the full amount of the contribution.

The House bill did not limit IRAs. The Senate, looking for additional revenue to preserve tax advantages for business, eliminated them for everyone but individuals not covered by other pension plans.

When time came to reconcile the two bills in conference, House members pushed for preserving the popular deduction on the grounds that the Senate version would penalize some low-income Americans whose non-IRA pension coverage was inadequate.

But new revenue estimates indicating that the tax bill would increase the federal deficit emerged during the conference, sending the conferees searching for more money. Various compromise proposals flew back and forth between the House and Senate negotiating teams.

At one point in the secret meetings, Treasury Secretary James A. Baker III suggested retaining IRAs without limit for two years, then repealing them outright, according to "Gucci Gulch" authors Jeffrey H. Birnbaum and Alan S. Murray.

House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) rejected the plan.

In the end, deductible IRAs were preserved for two categories of taxpayers: workers not covered by another pension plan, as in the Senate bill, and for those whose incomes were below a certain level (with partially deductible IRAs for incomes a bit higher), a concession to the House and to pro-IRA senators.

The resulting form -- new this year -- has 13 lines and requires six mathematical computations, not including the numerous calculations required by the 1 1/2-page IRA work sheet.

"We did neither this nor that," said Sen. Bob Packwood (R-Ore.), who chaired the Senate Finance Committee during the tax negotiations in 1986.

"We did not keep IRAs the way they were, we did not wipe them out. That is complex, but it was between phasing them out and keeping a sufficient amount to get support."

Despite this and similar traumatic battles over other provisions, the IRS estimates that 3.2 million taxpayers will find their forms easier to fill out this year. They are the beneficiaries of the increased standard deduction, which will allow them to shift to one of the short forms, the 1040A or the 1040EZ, from the longer return.

Another 2.5 million low-income Americans no longer will have to file a tax return because the higher personal exemption will put them below the income threshold at which tax is owed.

However, the IRS anticipates that 3.3 million additional returns will be filed by people who have been claimed as dependents in previous years and no longer can do so.

The IRS says it will deal leniently with taxpayers who make mistakes on their forms this year. Commissioner Lawrence B. Gibbs says the service will not impose penalties on taxpayers who make errors based on incorrect advice provided by the IRS' telephone-assistance service, and the IRS also is looking into waiving interest owed on the additional tax. Nor will taxpayers who had too little in taxes withheld from their paychecks last year be penalized.

Many taxpayers will find a pot of gold at the end of their tax-form travails this year: Although 1987 is a year of transition into the new tax system, more people will experience tax reductions than will pay more.

"In terms of the law's complexity, I think people make judgments based on what they have in their pocket at the end of the year," Bradley said.

"For 69 million people making less than $60,000 a year, they will pay less in tax than they did last year," Bradley added.

Taxpayers also can expect healthy refunds of the size they have become accustomed to, according to the IRS.

At this point in the filing season, the average refund is $781, although that could change.

Fewer than one-fourth of Americans have filed their returns, and Gibbs says "pockets" of taxpayers may find they have had too little withheld from their paychecks and will unexpectedly owe money.

Packwood believes that Americans only object to complexity when it does not help them cut their tax bills. When he makes speeches in Oregon, he often is asked why Congress produced a law that led to such dreadful tax forms.

Packwood responds that the law actually made the tax code much simpler because it removed the special low tax rates for capital gains, a major break for well-off Americans. The questioner usually looks startled at Packwood's reply, then says, as Packwood tells the story, " 'I didn't mean THAT kind of complexity.' "