Congressional auditors checking for government payroll cheats have discovered, instead, that bureaucrats regularly put in between $600 million and $800 million a year in overtime hours they are not paid for.

Contrary to the belief that many feds are chronically late, watch the clock and bug out early, the General Accounting Office says most civil servants work at least 40 hours a week. And a surprisingly large number put in extra time without charging Uncle Sam.

GAO investigators say the money "lost" from government workers who take long lunches, come in late or leave early amounts to between $85 million and $120 million a year.

The financial watchdog agency based its report on personal observation of randomly selected workers, records and interviews with supervisors. It studied more than 3,000 individuals - plus talks with hundreds of supervisors and union officials - in seven major departments. The departments covered - HEW, Treasury, Navy, VA, Army, Air Force and Agriculture - employ about 70 percent of the total federal civilian workforce.

GAO auditors, who are often very hard on personnel practices of other agencies, made the time study for Rep. Gladys N. Spellman (D-Md.). Spellman heads the House compensation and employee benefits subcommittee. It has been investigating illegal overtime payments and also reports that many workers regularly exceed the 40-hour week without getting extra pay for it.

GAO investigators came up with some interesting work-habits data. If correct, it means the taxpayers are getting back much more from dedicated workers than they lose to clock-watchers, the chronically tardy or the two-hours-for-lunch bunch. Examples from GAO:

About 80 percent of all those studied in all agencies work at least the 40-hourr week.

Between 18 percent and 27 percent (using weighted averages by agency size) worked between 41 and 70 hours per week, mostly without collecting overtime.

Although a large number of executives not entitled to overtime regularly put in long hours, GAO said a large number of mid-level and low-level workers who are entitled to overtime after an 8-hour day regularly worked longer for no extra pay.

The biggest single employe excuse for being late to work is "bad weather." Traffic problems ranked second, and the third most popular reason for being late to work involved either family or personal illness.

In a self-designation form, 87 percent of the workers said they were never late during the two-week period surveyed. Another 10 percent admitted to being tardy at least two days in 10, often citing (in addition to the standard excuses) the belief that there was no important work waiting for them.

GAO put a dollar value of between $660 million and $800 million per year on overtime employes worked but were not paid for.

The taxpayers saved about $500 million last year as the difference between uncompensated overtime and time employes were paid for when they were late, took long lunches or left early.

GAO's spot-check shows that most workers police their own hours. It said supervisors "do not place high priority on monitoring work hours because they trust employes to follow policy, believe most employes work 40 hours a week, and make up any lost time, and believe deadlines are met."

The Spellman subcommittee will look into the GAO data which indicates that much of the uncompensated overtime performed by rank-and-file employes may violate federal law. It is also concerned that some employes may be coerced into working overtime by bosses who refuse to pay them for it.

The GAO concluded that agencies should devise or improve ways of scheduling work so that employes have enough time to eat. It is also concerned that nonabusers and taxpayers have to make up - either in time or money - for employes who are not putting in the required time.