What do the D.C. Government's Department of Employment Services, Army's New Cumberland (Pa.) Depot and the Federal Highway Administration unit in Kuwait have in common? Two things:

First, all three have asked for permission to let long-service staffers retire early so they can avoid the necessity of firing relatively new employes.

Secondly, all three requests are likely to be rejected by the Office of Personnel Management, which on May 1 further tightened already-tough Reagan administration rules affecting early retirement for feds.

During the Carter years, federal agencies had an easy time getting OPM permission to let people retire -- some as early as age 43 -- on immediate annuities. OPM can authorize early retirement for workers with 25 years' service, or at age 50 with 20 years' service, if their agencies are undergoing major reorganizations or RIFs.

When the Reagan team came in it decided, at the urging of Congress and the General Accounting Office, to make it tougher for agencies to let people volunteer for early-out. They revised Carter-era rules that allowed long-service workers to voluntarily leave early because of reorganizations, even if no layoffs were contemplated.

This month the administration has screwed the early-retirement lid on even tighter. OPM now requires agencies to calculate what additional costs will be added to the Civil Service Retirement Fund; prove that 10 percent of their jobs are to be abolished or transferred, and further prove that at least 3 percent of the employes in the "affected component" face RIFs. All that means that agencies with post-May 1 requests pending will have a tough time getting approval, whether they be in the District of Columbia, Pennsylvania or Kuwait.