In the past four months, federal and postal workers have invested $264 million of their own money into their company, the U.S. government, as part of a new tax-deferred thrift savings plan. As of yesterday, the savings accounts of the nearly 1 million civil service investors were worth $555 million. That includes money contributed by the government plus interest they have earned -- currently 8 3/4 percent -- from the Treasury Department.

Thrift savings plan accounts were automatically opened for 588,956 employes hired since January 1984. The government also contributes an amount equal to 1 percent of pay -- retroactive to the date of employment -- for each of those new employes, regardless of whether they contribute to their own accounts.

Included in the automatic accounts, to which workers contribute nothing, are 196,524 of the new employes covered by the Federal Employees Retirement System who are contributing through payroll deduction to the generous tax-deferred plan, which allows them to invest up to 10 percent of pay and get a 5 percent match from the government.

The nearly 2 million federal workers hired before 1984 who are covered by the old pension plan can also participate in the tax-deferred savings plan. But their contributions are limited to 5 percent of pay with no government match. The Federal Retirement Thrift Investment Board, which manages the program, says that as of yesterday 347,569 of those employes have joined the investment plan.

All money invested this year goes into guaranteed Treasury securities. Over the next few months, the board will select a firm or firms to provide "investment management services" for an expanded program next year that will allow employes to put up to 20 percent of their total investments in a stock-market fund or a fixed-income fund. In future years, amounts workers can shift from the Treasury fund will be increased.

If Elected . . .

Three presidential candidates have responded to a pro-civil servant pledge written by the Public Employees Roundtable, which is eager to get all candidates on record as being friends of civil servants who won't attack them during the campaign.

The group says its proposed policy statement has been endorsed by two Democratic candidates, Sen. Albert Gore Jr. (Tenn.) and former Arizona governor Bruce Babbitt, and that former Delaware governor Pierre S. (Pete) du Pont IV, a Republican, expressed deep appreciation for the work of public employes.

Federal workers with long memories recall that in 1980 two of the candidates, Democrat Jimmy Carter and John B. Anderson, an independent, said that if elected, they would eliminate one of the two cost-of-living adjustments that government retirees received each year. In a statement issued for Ronald Reagan, but not by him, the Republican candidate promised that the twice yearly COLAs would remain if he were elected. Shortly after taking office, President Reagan with the support of the Democratic Congress, put federal retirees on a schedule of one COLA per year.

In 1976, candidate Carter promised federal employe unions he would back two major legislative initiatives, only to reverse himself as president.

Magazine Folding

Pentagon budget cutters have decided to stop publishing the Defense Management Journal, the scholarly award-winning magazine that covered subjects from computers to managing sick leave. Defense considers the publication too costly.