Mandatory social securtiy could be a blessing or a bummer for federal workers. It depends on how much money you make.

Employes retiring on salaries of $25,000 or less would get slightly larger benefits it their Civil Service Retirement System is blended with social security.

But federal and postal aides making $25,000 or more -- and that includes nearly half of Washington's white-collar workforce -- would get reduced annuities because of "income redistribution" feaures the Social Security system would bring with it.

A blue-ribbon panel from the Department of Health, Education and Welfare made its report to Congress yesterday, outlining options Congress and the White House have if they want to extend social security to 2.6 million federal and 3 million state and local government workers.

Backers of mandatory social security coverage for the bureaucracy argue that feds -- who are suspicious of any merger -- have nothing to fear. But some do. Lower income persons would get higher benefits but higher income federal workers could get lower annuities when they retire if the system is adopted.

Social security's higher percentage of retirement payout to people who had lower incomes is a feature unknown to the federal staff retirement program. Under social security, individuals with the highest salaries and highest contribution rates get back proportionately less when they retire and begin collecting social security, than do lower-income persons. By contrast the regular Civil Service program -- a staff funded system whose benefits are taxable -- is based strictly on longevity and salary. The more you make and the longer you work for government the bigger your annuity.

Here, using official government figures, is how the CS retirement system works now; and what benefits would look like if Congress and the White House decide to extend mandatory social security coverage to the federal workforce:

A long-service federal worker retiring after 40 years service, at age 62, can now expect to get an annuity equal to 71 percent of his final pay -- based on his/her high 3-year salary.

Under the offset provisions of dual coverage, under both social security and CS retirement, a worker retiring with a $10,000 salary average would get 45 percent of his salary from the CS fund, and 33 percent from social securtiy. That would amount to 78 percent of salary, as opposed to 71 percent under the current system.

An individual retiring from goverment with a $20,000 average salary would -- under a combined pension system -- get 23 percent of salary from social security, and 50 percent paid from the CS fund. That is 73 percent of salary.

The $25,000-a-year retiree would get 71 percent of salary as an annuity; 18 percent from social security and 53 percent from the CS fund.

But the person retiring on a $30,000 average federal salary would get only 68 percent of it in annuity. Fifty-four percent would come from the CS fund, and 15 percent from social security.

The "tilt" feature in favor of lower-income persons in social secutrity could have an impact on members of Congress who must pass or reject the plan. They are high-income -- $60,622.50 a year salary -- federal workers. And they are under an enriched version of the CS retirement program. Unless Congress voted special benefits for itself, or elected to remain outside of the social security system, the members would be voting smaller future annuities for themselves by approving a link-up between social security and the civil service retirement system.