Most retirement-age workers would have to retire by Oct. 31 to qualify for lump-sum pension payments. But there is a very slim chance that people who won't qualify for retirement until the end of the year may be able to take the popular option that is selected by nearly 80 percent of retirees.

Differing Senate and House budget plans call for ending the lump-sum pension option as of Nov. 1. The two-part lump-sum payments represent about

7 percent of the retirees' lifetime federal salaries. People take the lump sum, although most of it is taxable and can reduce the lifetime monthly pension check by 20 percent or more.

The House Post Office and Civil Service Committee plan would suspend the lump-sum pension option for five years starting Nov. 1. During that period, only retirees 65 or older with 30 or more years of service could get lump-sum payments. The five-year suspension would save the government an estimated $1.7 billion and protect retiree cost-of-living adjustments from being frozen or trimmed next year.

The Senate Governmental Operations Committee plan would eliminate the lump-sum option permanently as of Nov. 1. If either plan becomes law, that means an Oct. 31 retirement deadline for many people. Lump-Sum Long Shot

There is a slim chance that the lump-sum deadline could be extended through the end of November or even December. The federal employee portion of the budget plan actually exceeds dollar cuts assigned it by the budget summit. Rep. William D. Ford (D-Mich.), a staunch friend of federal workers, is chairman of the Post Office and Civil Service Committee. He's expected to push budget negotiators to extend the lump-sum qualification deadline past

Oct. 31 because workers have not known what the new rules are going to be. But that is a long shot, and insiders say that to be sure of getting the lump-sum payment, be prepared to retire by Oct. 31. Retiree COLA

Neither budget plan would freeze or delay cost-of-living adjustments due federal-military retirees in January. Based on the countdown to date, that COLA will be worth at least 4.9 percent. It could be more. January Pay Raise

The budget talks should not have any impact on the January pay raise due white-collar federal workers. President Bush had proposed a 3.5 percent adjustment. However, House and Senate Appropriations Committee conferees yesterday approved a 4.1 percent raise. The increase is on par with raises in the private sector last year. The president is expected to issue an executive order in December that would raise salaries for members of the Senior Executive Service from 18 percent to almost 25 percent. The proposed new rates were listed here Oct. 11. Job Mart

The Office of the Secretary of Defense has a temporary opening for a Grade 11 ($29,891 per year) public affairs specialist. Call 202-619-2274.

The Energy Department needs a GS 13 ($42,601) telecommunications specialist. Call Velma R. Washington at 202-586-9842.