The General Accounting Office said yesterday that 1 million federal workers who were erroneously overpaid about $8 million earlier this year don't have to give the money back.

Most employes probably didn't take much notice of the overpayments, which amounted to between $6 and $14 per worker.

GAO's decision, released yesterday by Rep. William Ford (D-Mich.), is apparently the last stop in a payroll roller coaster ride the government has been on for several years in the name of economy.

As part of a "temporary" program to save money, Congress told agencies several years ago to stop figuring salaries based on a 2,080-hour year and to compute them instead on the basis of 2,087 hours. The changeover trimmed several dollars on average from employes' paychecks.

Because the payroll change went into effect at the same time workers got an across-the-board pay raise, many didn't notice the difference, although the change saved the government millions of dollars each month.

That accounting procedure expired last year. Congress made it clear that it planned to make the change permanent, but delayed restoring it for several months.

During that period, half a dozen agencies quickly reverted to the previous accounting method. Among them were the Health and Human Services and State departments, the General Services Administration, Federal Communications Commission and the Defense Contract Audit Agency.

When Congress switched back to the new accounting system, those agencies that had made the change in a timely manner wound up temporarily shortchanging their employes. Two weeks ago, the GAO ruled that those employes were due back pay, averaging about $90.

Yesterday's decision involves those agencies with most of the federal work force that either didn't make the switch or made it late, and, as a result, overpaid their employes.

Ford, who chairs the House Post Office-Civil Service Committee, didn't think workers should be forced to give the money back, and asked GAO for its opinion.