FOR THE PAST 20 YEARS

, Larry Rosenwald, an English professor at prestigious Wellesley College, has been playing hide-and-seek with the IRS.

Each year, Rosenwald and his wife, a self-employed piano teacher, file a tax return but omit to pay a portion of their tax bill. Specifically, they withhold 30% of what they owe. This, according to the War Resisters League, an antiwar activist organization, is the portion of personal income taxes that the government dedicates to current military spending. (The official figure is 20%, according to the White House's Office of Management and Budget, based on funds collected through Social Security taxes as well as income taxes.)

"As pacifists, we can't bring ourselves to pay for those expenses freely," explains Rosenwald in a letter that he attaches to his tax return. Instead, he continues, he and his wife will deposit the refused taxes in an account where the interest on the deposit will be used for causes they support through donations to small grassroots organizations that do peace and environmental work.

Usually within a year, the IRS levies Rosenwald's salary or bank account and takes what it's owed plus penalties and interest.

It may not be an efficient way to curb the government's military spending, Rosenwald admits. But throughout the country there are an estimated 8,000 or 10,000 people who, like him, avoid the tax system in the same way.

War tax protesters have been around for decades: The longest publicized streak belongs to now 83-year-old Juanita Nelson of Deerfield, Mass., who has been refusing to pay income tax since 1947. But not surprisingly, the numbers while always small typically grow when the United States is at war.

Since the war in Iraq started in 2003, the number of folks interested in war tax resistance has been on the rise, says Ruth Benn, head of the National War Tax Resistance Coordinating Committee (NWTRCC), a New York-based group that, since 1982, has worked to coordinate the activities of war tax resisters throughout the country. Although no hard numbers exist on how many tax payers are planning or have already become tax resisters since 2003, Benn looks for proof in the number of visits to the organization's web site. While the site used to get just 50 hits a day (before Iraq), it's averaged 500 a day since then. As tax time approaches, the site is now up to 1,000 hits a day.

Just how they approach war tax resistance varies. Some folks refuse to pay a portion of their tax bill. Others, like Benn, refuse their whole tax bill. Most war tax resisters also donate their unpaid taxes to charities they like, often in organized events on April 15 (or whatever date tax-day falls on, this year that's April 17).

No one knows for sure just how much tax resisters have refused over the years, or how much has been collected back, says Benn. Based on surveys the NWTRCC has done among its members, she estimates that in all, the IRS collects probably half of what war tax resisters don't pay. "I've certainly resisted more than they've ever collected, and I think that's true in terms of all tax resisters as a group," Benn says.

Benn, a resister since 1987, refuses 100% of her taxes. She believes that refusing just the portion that equals the government's war spending doesn't guarantee the government won't spend her taxes on war anyway, she says. She avoids IRS collections easier than others because the NWTRCC, where she works part-time as a consultant, doesn't honor IRS levies. (Technically, the IRS could try to collect from NWTRCC just like it collects from individuals by taking the money out of the organization's bank account but that hasn't happened, Benn says.) As for her other work, which she does on a freelance basis, she says "the IRS could send a levy, and in that case I'd probably just quit the job and find something else." It's what many war tax resisters do when their salaries get levied, she adds.

Like many war tax resisters, Benn doesn't own any real estate or other large assets, and keeps her bank account balances low enough to not collect any interest. (She does this so that the bank doesn't report her accounts to the IRS, making it easier to collect.)

Keeping your money "under the mattress" in cash, and not in the bank is one way to avoid the eyes of the IRS, says Frederick Daily, a tax attorney and author of the book "Stand Up to the IRS." "I actually tell my clients who owe the IRS to do exactly that," he says. That's not to be confused, though, with lying to the IRS about your assets in the event they come knocking on your door or summon you to court, he adds. That's illegal.

Likewise, not filing a federal tax return is a crime punishable by up to one year in prison for each year you don't file and have a tax liability, says Daily. (How often this is actually enforced is another question entirely. Although tax evaders can and do go to prison, the government simply doesn't have the man power or funding to prosecute everyone.)

Folks who do file but don't pay, on the other hand, are easier to find, as the IRS has an automatic system to kick out unpaid tax returns, according to Daily. These nonpayers are subject to penalties and interest of up to 75% of the unpaid amount, which the IRS can recover by wage or bank account levies, or even asset seizures. (There is a 10-year statute of limitations, which means the IRS has 10 years to collect your tax due from the date they receive your tax return.) In addition to that, the IRS can impose a fine of up to $5,000 for what it calls "a specified frivolous submission," including refusing to pay taxes because of disagreement with the government's use of tax revenues. Those who pursue such cases in court could face additional penalties of up to $25,000.

The taxes refused by war tax resisters are part of the so-called tax gap, which is now an estimated $290 billion a year. But it's still a tiny if not negligible part, says William Raabe, a tax professor at Ohio State University who has written about tax audits and administration of the tax law. Even if war tax resistance has become more popular in the past several years, Raabe estimates that probably 1% of all nonfilers are tax resisters, and war tax resisters are a subset of that. "These are very small numbers, [considering] this year there will be over 140 million 1040 filers," he says. (The other 99% are part of the "underground economy," i.e. folks who are paid under the table.)

This might explain why the IRS rarely, if ever, goes after war tax resisters other than by imposing levies and tax liens. The IRS says it treats war tax resisters just the same as anybody else who doesn't pay taxes.

"Most consequences [for war tax resisters] are in the administrative or civil arena," says Peter Goldberger, a criminal defense lawyer in Ardmore, Penn., and pro-bono legal counsel for war tax resisters. "In the 25 years that I have been one of a small handful of lawyers in the country interested in helping these people, I know of one or two criminal cases."

Since 1942, the IRS has brought court action against 47 war tax resisters, according to the War Resisters League, which keeps a record of such cases. Most recently, three small-business owners in Mays Landing, N.J., were found guilty of income-tax evasion and failure to file and were sentenced to six, 24 and 27 months in prison, respectively. In that case, however, the three individuals, who are members of a pacifist religious group, refused to file federal income and Social Security taxes for employees of their business who were also members of that group. This, and not the fact that they did not file their individual taxes, resulted in the sentence, according to Goldberger.

And then there are war tax resisters who manage to not pay tax perfectly legally, by deliberately earning such a low amount of income that they don't owe the IRS a dime. Dave Gross, 37, quit his $100,000-a-year job as a technical writer in San Francisco as soon as the war in Iraq started in 2003, just so he wouldn't have to pay taxes. Now working as a freelance writer, Gross makes sure his income is low enough to not have a tax liability. "I've been working more or less full-time for four months out of the year," he says. "Then I just live off what I have squirreled away from that."

In 2005, Gross earned $27,975 on which he owed $0 in income tax thanks to deductions like an IRA, Health Savings Account and a retirement contributions credit. He does refuse self-employment taxes, but makes sure he has the funds available in his bank account, should the IRS comes to collect. He admits that living on this limited income hasn't been easy. To lower his monthly living costs, Gross first moved to Oakland, then back to San Francisco, where he now lives in Inner Richmond, where rental prices are lower. "The biggest sacrifice is I hardly eat out any more," he says. "But I've learned to enjoy cooking." It's all worth it, he says, to live in harmony with his principles.