Federal managers may be handing out millions of dollars worth of unnecessary lifetime cash awards to employes when a certificate, or one-shot bonus would do just as well. That is one of the conclusions of a General Accounting Office study of the government's multimillion dollar incentive awards program.

GAO said some bosses apparently recommend workers for quality step increases, which, in effect, are lifetime pay raises, when it would be just as effective and much cheaper to give the civil servant a single bonus or award.

The one-shot payments are just that But quality step increases -- moving an employe up a pay notch within his or her grade -- have a lifetime benefit to the workers. And a long-term compounding cost to the government.

In fiscal 1977, GAO said, U.S. employes got $34 million in quality pay increases. But the compounding effect of those increases to date, GAO reckons, has cost as much as $138 million.

In addition to overuse of the quality pay increases, GAO said many federal managers surveyed did not really understand the program or their options in rewarding employes. Also, GAO said, many agencies pass the recommendations for awards too far up the line, to officials or committees, rather than giving the managers the chance to give awards to their immediate subordinates.

GAO recommends that the Office of Personnel Management set up new guidelines -- under the civl service reform act -- to encourage agencies to give the right kind of awards to the right people within their own framework for recognizing outstanding performance. It says it could mean more one-shot rewards, increased productivity and lower cost in government.