Senate-House conferees begin work this week on a compromise tax reform bill that is almost certain to make a major change in pension tax rules for 20 million workers. Among them are federal, state, local government and private sector workers who contribute to their retirement plans.

Both the Senate and House have approved tax reform bills that would eliminate the so-called three-year recovery rule. It allows retirees to recover all their previously taxed pension contributions without paying additional federal taxes. It takes about 18 months for the typical government retiree to get back those contributions.

That recovery period is an important part of retirement planning for many people. During the period, many workers take second jobs and cash in stocks, individual retirement accounts or U.S. savings bonds. Because their pensions aren't considered taxable income during the recovery period, other earnings or income are taxed at lower rates.

The House tax plan would eliminate the three-year recovery rule, retroactive to July 1. If that version becomes law, anyone retiring now would have to pay taxes right away on a prorated portion of the pension, based on life expectancy.

The employe contribution of approximately 7 percent would not be taxed, but the government contribution would be subject to the prorated tax.

Under the Senate plan the recovery rule would be phased out over a two-year period starting in January 1988.

The change would mean that retirees would begin paying taxes much sooner than anticipated although their overall tax burden in the long run would not be any greater.

Federal and postal unions, professional organizations representing U.S. workers and others affected by the proposal, all object to any change in pension tax rules and have pledged to fight the change during the conference sessions.

But if they lose, and odds are they will, they say they would prefer the Senate version because of its later effective date.

The Senate is expected to appoint 11 members to the conference from the Finance Committee headed by Sen. Bob Packwood (R-Ore.). House conferees will come from the Ways and Means Committee and be appointed by its chairman, Rep. Dan Rostenkowski (D-Ill.). Backers of overall tax reform say it will be weeks, at least, before any compromise bill is approved.

If a pension tax change is approved, it will affect all federal workers, including current members of Congress. While it is possible that the pension tax change will be dropped from the final tax reform bill, chances are the change will be made.

There is good reason to believe that any pension tax change will not be retroactive. Many popular and influential members of Congress, including House Speaker Thomas P. O'Neill Jr. (D-Mass.) and Sen. Charles McC. Mathias Jr. (R-Md.), are retiring early next year, and Congress has been known to protect its own. People

John C. Yazurlo, deputy inspector general for the Department of Education, is retiring next month. His 29-year career includes service at the Federal Aviation Administration, the General Accounting Office and Housing and Urban Development.

Navy's Freda W. Kurtz has been elected president of Federal Employed Women Inc. Other officers are Lt. Cmdr. Ann C. Greiner, Shirley Radcliffe, Martha Lyle, Patricia A. Pierstorff, Beatrice Bolds, Jean Christiansen and Mary B. Holzer. FEW's national convention will be July 23-26 in Las Vegas.