Federal workers have until Nov. 30 to retire and qualify for the lump-sum pension option. Afterward, the popular benefit will be eliminated for five years for most employees. That's official.

Congress finally set the new lump-sum rules as part of the budget reconciliation act it approved during the weekend.

Without the act, the lump-sum option would have disappeared this month. The extra time to qualify for the benefit is expected to push thousands of workers into retirement next month. It came just in time for District government employees who are under the Civil Service Retirement System, who have just been given a special early retirement offer that runs from Oct. 26 to March 31.

About 80 percent of all federal retirees take the two-part payments, which equal the retiree's contributions to the pension plan. Payments can be as much as $100,000. For the typical retiree, the lump sum is about $32,000 before state and federal taxes. Taking the benefit reduces the retiree's lifetime annuity (depending on age and length of service) by from 5 percent to more than 20 percent.

During the five-year benefit suspension, the lump sum still will be offered to workers who lose their jobs because of no-fault involuntary separations, such as reductions-in-force or job abolishment. It will not be available to members of Congress, people in executive schedule jobs, non-career senior executive employees, non-career senior Foreign Service officers or political appointees.

Under the new rules, the 50/50 lump-sum payments will be made 12 months apart. That will prevent most people from getting two payments in one calendar (or tax) year. Before the change, retirees got their first lump-sum payment anywhere from a few weeks to several months after retiring and the second payment one year from the date of retirement. Under the new rules, retirees will get their second payment one year after the first payment.

Because of the complexity of the new lump-sum rules, here is the official conference language supplied by the House Post Office and Civil Service Committee. Its chairman, Rep. William D. Ford (D-Mich.), fought to give employees the extra time to retire. Here are the new rules:

"The alternative form of annuity {lump sum} will be suspended for five years through fiscal year 1995. As a consequence, any federal employee who wishes to elect the 50/50 lump-sum payment option must separate from service no later than Nov. 30, 1990."

Employees eligible to take the lump-sum payment during the five-year suspension include:

Workers called to active duty before Dec. 1, 1990, as part of Operation Desert Shield, and Defense Department civilians asked to stay on in support of Desert Shield. Both groups of employees must have been eligible to elect the lump-sum option before Nov. 30, 1990.

People who retire (except on disability) with a life-threatening medical condition. They will be entitled to get a 100 percent lump-sum payment.