Loudoun County Administrator Philip A. Bolen and his staff have five weeks to design what they describe as the most significant downsizing of the county government in its 233-year history.

At the direction of the Board of Supervisors, the staff will be looking for up to $12 million in potential cuts from existing programs and services for fiscal 1992, not counting a major scaling back of education funding that the supervisors also have suggested.

The county government and school reductions go beyond trims already attributed to state funding cutbacks. They go beyond anticipated cuts eliminating local spending on construction programs and raises for county workers.

Layoffs are all but guaranteed. Next year's adopted budget probably will be smaller than this year's, Bolen says. That represents a dramatic change of direction for a county government that experienced a 30 percent increase in spending from fiscal 1990 to fiscal 1991.

The ultimate decisions will be made in about three months by the Board of Supervisors, but Bolen's 1992 budget proposal is scheduled to be delivered to the printer at the end of February and to the supervisors by mid-March for their deliberations.

Although this year's budget has been balanced by cutting almost $8 million from the $273 million plan approved last spring, next year's budget will be a nightmare, many officials predict.

Sinking real estate assessments and other economy-related factors have fueled projections of a massive deficit. The Board of Supervisors has set the maximum potential tax rate for real estate at $1.05 per $100 of assessed value, but the supervisors want to see a list of cuts that would allow the rate to be as low as the current 85 cents.

Bolen has warned that such cuts would be painful to the supervisors and their constituents. Because commercial and industrial assessments are declining and residential assessments will be almost unchanged this year on average, "homeowners will be shouldering a larger share of the tax burden, regardless of any change in the tax rate," Bolen recently told a state legislative committee.

Additional revenue sources to the Loudoun government are contemplated during or after fiscal 1992, but some depend on General Assembly action. A countywide restaurant meals tax, a local cigarette tax and a local income tax surcharge may be considered at some point, officials say.

On Tuesday, the School Board received the school administration's proposed spending plan for next year, with dramatic cuts forecast in a wide range of programs. Adoption of the school budget is expected in late February. By law, Bolen's overall budget presentation to the Board of Supervisors must include the School Board's spending proposals, but the supervisors can increase or decrease total funding for education.

Bolen and his staff are gearing up the search for cuts following Bolen's first formal personnel evaluation in his nearly two decades as administrator. Although the Board of Supervisors termed his performance "better than satisfactory" at the end of a grueling review process, the board refused to give him an employment contract, citing the overall budget crunch.

Bolen's salary was increased 5 percent, retroactive to July 1, 1990, which boosts his annual pay to nearly $86,000.

The public will get an early chance to comment on its wishes for the 1992 budget. Next Thursday, the Board of Supervisors will hear residents' comments on suggested cuts and real estate tax levels for the coming year. That session will begin at 7:30 p.m. in the board's meeting room at 18 N. King St. in Leesburg.

There will also be the usual public hearing on the budget after Bolen's proposal is made public.

Already, taxes and spending have taken a front seat in this election year. Last week, a nonpartisan political action group calling itself Taxaction '91 announced that it will work for candidates in this fall's Board of Supervisors elections who favor limiting real estate tax increases and cutting spending dramatically.

County officials have brought in a part-time adviser at a cost of roughly $2,000 to guide the administration on proper procedures for cutting back the staff. The layoff process would have to begin in early April for county workers and school employees for the layoffs to take effect at the beginning of the new budget year, officials say.

Salaries and benefits make up a large portion of the county government budget and the vast majority of the education budget.