The number of sick days that federal employees take, which now costs the government more than

$2 billion a year, jumps dramatically before retirement, according to a new General Accounting Office report to Congress.

GAO's study was limited to the General Services Administration, which has one of the highest sick leave rates of any federal agency or department. But it could be used by critics of the federal fringe benefit system who want to reduce the amount of leave that employees get or introduce safeguards to discourage heavy sick leave use just before retirement.

GSA is the government's housekeeping agency. It has the largest number of employees in government who have little or no sick leave left by the time they retire, according to GAO.

The typical civil servant is entitled to 13 days of sick leave a year and uses about 6.8 days, GAO said. Unused leave can be carried over from year to year. When employees are otherwise eligible to retire, they can boost their annuities by counting sick leave as additional service time.

GAO looked at sick leave use of more than 300 GSA employees in the Washington area plus Philadelphia, Fort Worth and Kansas City, Mo., who retired in 1985. The congressional watchdog agency said average leave use for those workers jumped in the last year of service. More than half took three months (the average was 66.1 days) of sick leave just before retiring.

The report said that while Congress allowed sick leave accrual in order to give employees a reason to use it wisely, many workers have found an incentive "to use all of their sick leave before retirement because they receive full pay while on leave, which is greater than their retirement annuity would be for the period, as well as receive service credit for the sick leave used." GAO said that changes in sick leave credit policies under the new Federal Employees Retirement System, which covers most people hired since 1984, mean that workers under FERS "will have a greater incentive to use their sick leave before retiring."

To anticipate a question lots of federal workers in other agencies may want to ask: GAO did not release any statistics of sick leave use at GAO. New Publications

Workers worried about losing their jobs to contractors may want to look at a new (free) publication from the American Federation of State, County and Municipal Employees. It's called "Government for $ale." It deals with the trend of federal, state and local governments to contract out work and with some of the ways that public employee groups have countered such actions.

The 1988 version of the Federal Employees Almanac has just been published. The 244-page book updates federal pay, leave and retirement rules, and it has pay tables for all employees. It is published by Joseph Young, former federal columnist for The Washington Star, and Don Mace, formerly an associate editor with Federal Times. Single copies are $3.95 from the Federal Employees Almanac, P.O. Box 7528, Falls Church, Va. 22046-1428.