When she walked out of the main meeting room of the William Penn House at 515 E. Capitol St. the other evening, April Moore was much calmer and more confident than when she went in. For two hours she was part of a group discussion on a subject that for the past year has dominated her thinking: military tax resistance.

Moore, 28, a free-lance writer who earns about $10,000 annually and lives in the Adams-Morgan section of Washington, has paid no federal taxes in a year. tShe is opposed in conscience to military spending and refuses to give the Internal Revenue Service any money at all.

What she does give the IRS is a "long, from-the-heart" letter attached to her quarterly forms for estimated earnings.Moore wants the government to know that she is a tax resister , not a tax evader or cheater.

The distinction, which dates to the 1750s when Pennsylvania Quakers said nay to taxes for the king's army to wage the French and Indian War, means that she is neither hiding from the law nor trying to beat the system dishonestly.

"Of course you are scared when you do this," Moore said after the meeting in which the gathering of 30 was counseled on the legal intricacies of taking this kind of moral stand.

"You think you'll be hauled off to jail. One part of me says to keep quiet about what I'm doing. But another part of me says, speak out and be proud of not putting up money for war."

Moore's calmness came in knowing that she wasn't alone in her convictions. In fact, those familiar with the national network of peace groups say that war tax resistance is a fast-growing movement.

"Something is definitely happening," says Bill Samuel, who led the discussion at the William Penn House and is on the task force on war taxes of the Balitmore Yearly Meeting of the Religious Society of Friends. "In just the past year or so, my group has been getting a lot more inquiries. It's year-round, and not just during the tax filing season."

The War Resisters League in New York estimates 2,000 to 10,000 citizens nationally who refuse to pay part or all of their taxes because of opposition to military policies. The range is large because of the uncounted resisters who live on nontaxable income or file no return at all.

With the Reagan administration calling for large increases for the Defense Department, Samuel says he and his group expect to be busier than ever counseling war tax resisters.

"The IRS is not predictable," he says. "It's not an absolute rule, but if you're open and tell the IRS what you're doing, it won't prosecute."

At the IRS, spokesperson Ellen Murphy says the agency "is interested in the civil liability aspects of these cases: in other words, getting the money. The Justice Department decides whether or not to criminally prosecute. War tax resistance is not as widespread as other forms of protest. But it's a serious matter. It's an attempt to illegally avoid payment of taxes. If 93 million citizens are paying voluntarily, we're obligated to look at at those who don't pay, whatever the reason. No constitutional right exists not to pay taxes."

For most military tax resisters, especially those who act only after considerable inner wrestling with their consciences, the object is not to bedevil the IRS, but to demilitarize their governement.

"Confrontation is an important part of tax resistance," says Ed Hedemann of New York, who estimates he has denied the IRS $7,000 since 1972. "I'm interested in confronting the government."

Hedemann, in reporting that the IRS has yet to collect from him, admits with some pride to being a hard catch: "I own no property, have no bank account and my employers -- the War Resisters League -- won't cooperate with the IRS. The government seems to have given up."

How hard the IRS looks is an open question.

William Durland, a constitutional lawyer who serves as the legal counsel for the Center on Law and Pacifism in Philadelphia, wrote last year in "People Pay for Peace: A Military Tax Refusal Guide" that he knew of no criminal cases between 1972 and 1978 and only two since 1978.

"The fact that so few have been arrested shows that there has been no (IRS) policy to crack down," Durland writes. Something else to keep in mind, he suggests, is that the "government by no means collects all unpaid taxes. Many defaults are never followed up, while others are merely looked into and let alone."

One reason that April Moore is not only not in jail, but has yet even to hear from the IRS, is that the agency's collection costs may be higher than what they would get in hot pursuit.

War tax resisters use several options. Some file their 1040 form and refuse to pay a percentage -- about 33 percent -- corresponding with the total military expenses, or the current defense budget, or only what is spent on nuclear weapons. Whatever the withholding comes to, the sum is listed in the "itemized deductions" section of Schedule A.

Others use the Washington War Tax Resistance guide, which suggests an eight-step process, beginning with a routine filling out of the 1040 through line 32.

Others take extra deductions on the W-4 Form. "Last year, I took four extra deductions," says Delia Miller, a research assistant. "With a total of five exemptions, myself included, I kept the government from automatically withholding the taxes from my paycheck. In that way, I can send the money to the Fund for Life which uses it for peaceful purposes."

Miller filed last April. It wasn't until July that the IRS contacted her. It was a "Dear Taxpayer" letter saying deductions for protest purposes were not allowed by law. A computation of her due taxes, plus 12 percent interest was included. A few weeks later, Miller sent in what she owed.

Miller plans to resist again next month, and in her words, "perhaps hold out a little longer."

Veteran resisters who have grown accustomed to the ways of the IRS, often go the distance, i.e., through the tax courts, appellate courts and on to a Writ of Certiorari with the Supreme Court. The high tribunal has yet to grant a writ, much less rule in favor of tax resistance. But in a 1979 petition to the court, Howard and Barbara Lull of North Carolina explained the basic philosophy of the movement:

"Those who will not recognize the linkage between war taxes and murder have either sold or buried their consciences or have never been exposed to this obvious relationship . . . Up to this point the courts have decreed that Christian pacifists must pay for the killing of the innocent. (We) say 'no,' as do many others . . . That only a small number of Christians subscribe to the obvious does not reduce its correctness.

"Nor should the growing recognition of the direct link of war taxes to bloodshed deter the Court from acknowledging the firepower of war taxes." The court refused to hear the case.

Long before thinking of a judicial remedy, from the IRS. If the agency's demand to pay up is not met and the resister does not begin an appeal process -- either within the IRS or through the courts -- liens, levies and seizures may follow. According to Washington War Tax Resistance:

"The IRS cannot proceed to forcible collection while you are engaged in administrative appeals or Tax Court action.They must send you a final bill giving you 10 days to pay before collection. They may seize delinquent taxes from bank account, salaries, or by auctioning property such as an automobile or real estate (rarely done). Collection may occur after considerable delay or not at all."

Resisting can be a high risk, as John K. Stoner, a Mennonite pastor in Akron, Pa., wrote last year in the Friends Journal: "War tax refusal is to disobey the government and thereby to bring down upon one's head the whole wrath of the state, society, family, business associates and probably God as well. . . . For the forseeable future, war tax resistance will be an action that is taken at some cost to the individual or the church institution, with no assured compensation except the knowledge that it is the right thing to do." n