Some U.S. workers can now retire as early as age 43 on immediate, but reduced, pensions if they are caught up in an agency or departmental reorganization.

A new "early out" retirement provision now is in effect as part of the Civil Service Reform Act. It allows employes in agencies undergoing reorganizations to retire at any age with 25 years service, or at age 50 with 20 years of federal or combined federal-military service.

The new provision could benefit thousands of people in months ahead as the Carter administration begins merging agencies and reorganizing others in earnest. Reorganizations are planned or rumored in HEW, Interior, Commerce, HUD, Defense and Agriculture, to mention just a few.

There will not be many retiring as early as age 43, but it is possible if the employe began in the military (as early as 17) or government at 18. Workers who do elect the early retirement will be penalized by a 2 percent reduction for each year under age 55.

Until the new law went into effect this week, that sort of early retirement was available only to employes in agencies hit by major RIFs (reductions-in-force). In addition, the RIF had to effect at least 5 percent of the agency's employes, and had to be approved by the Office of Personnel Management (formerly the Civil Service Commission).

Although the early retirement carries stiff pension reduction penalties for employes under age 55, it is still a generous new benefit and one rarely available to most private sector workers.

The normal age and service requirements for government are 62 with five years service; 60 with 20 years; 55 with 30 years or 50-20 for persons engaged in hazardous work. The 50-20 requirement, and 25 years at any age formerly applied only to special RIF situations.

Federal officials agree that the expanded early-out option for agencies undertaking reorganizations will cost the civil service fund more money. More employes will be retiring sooner and presumably earning benefits (even at reduced rates) for a much longer period of time.

Once it gets rolling, the new law will make it more attractive for relatively long service workers to quit during RIFs or reorganizations, minimizing the "bumping" effect of job changes on younger, less senior workers. It also will mean many more relatively young federal employes will be making second creers in industry, much as retired military personnel now do, to support themselves and their families.

The first federal operation to take advantage of the new liberal early-out policy is, ironically, the Office of Personnel Management. OPM is one of several spin-off agencies created by the demise of the Civil Service Commission.

The OPM is reorganizing, and is offering employes the option of retiring early during the period Jan. 15 to June 30. Those who exercise the option must be retired by June 30 of this year. Other agencies planning or in the midst of reorganizations will also make the option available.

Senior Executive Service: I understated two important figures yesterday in explaining the SES pay and bonus structure. The pay range for employes who go into the high-risk, high-reward service will be from $44,756 to $52,800. I said the top salary would be $47,500. Also, the maximum bonus available to executives will be $10,560 per year, not $10,000 as listed in the column.

Association of Federal Investigators: The government sleuths have picked Paul A. Adams, HUD's acting assistant inspector general, as president. Other officers are Lt. Col. Charles Perkins of the Defense Intelligence Agency; Federal Trade Commission investigator Ruth S. Sacks and Lyle E. Schmidt, a criminal investigator at HUD. Louis T. Williams is executive director of the AFI.

Protest Demonstration: Local union leaders in various federal agencies are planning a Jan. 25 demonstration here to show their unhappiness with President Carter. Many empllyes are upset by White House "caps" on white collar federal pay, and a 5.5 percent pay raise limit Congress slapped on government blue collar worker.