With much self congratulation, the Prince George's County Council cut the real estate tax rate by 10 cents yesterday, assuring that almost all property owners will have lower tax bills this election year.

Officials estimate that more than 97 percent of property owners will have substantially lower tax bills in Prince George's, where the real estate tax is one of the highest in the Washington area and has become a major issue.

The county's new tax rate of $4.04 per $100 of assessed valuation, combined with a statewide assessment rollback, will give the owner of a $47,000 home a saving of about $118 over last year's $971.90 tax bill.

Yesterday's 11-to-0 vote to cut taxes while funding a $443.5 million budget was the final act in a campaign begun in March by County Executive winfield M. Kelly Jr. with great fanfare and coinage of the slogan "Promises to Keep - True Tax Relief."

"Kelly promised it and we kept it," declared council member Gerald T. McDonough.

"This is an outstanding accomplishment," asserted council member Samuel Bogley.

Much of the tax reduction was made possible by the Maryland General Assembly, which changed the assessment percentage used in figuring taxes.New tax bills will be computed by multiplying the tax rate by 45 percent of a home's value, instead of 50 percent, the ratio used in recent years.

The cut in the county's tax rate came after months of revenue juggling and budget cuts by both the county executive and the council.

The council cut a total of $1.85 million from the proposed police, health, sheriff, corrections an school board budgets to produce the tax reduction.

By deleting a new elementary art program and canceling repair projects scheduled for two school stadiums, the council managed to trim $1 million from the total school budget.

Part of the cut also came from the replacement and maintenance budget for school supplies, a $200,000 reduction council member Francis B. Francois said "might be unwise.This could create fewer typewriters, fewer pencils. Are we sure we want to do this?"

Francois also argued against a proposed $109,000 cut in the sheriff's budget. The sheriff had asked the council for money for additional deputies for courtroom duty.

But sources said Kelly told the council members in an executive session earlier this week that he would veto any budget item that included new funds for the sheriff's department.

The council finally deleted the $109,000 for the sheriff but approved new programs in other areas.

The council added $40,000 for a new tourism program, $60,000 for MANDAT, an educational assistance program for people in the county's older neighborhoods, and $100,000 for health programs, including money for an expanded mental health program.

When Kelly sent the budget to the council in March, he highlighted several new improvements in county services. Two new libraries, expanded credit hours at Prince George's Community College, two new mobile intensive care units and more money for aging programs and public works were included.

The council, while cutting the budget in several areas, managed to keep these improvements in the budget for the fiscal year that starts July 1. The council did delete several new Department of Corrections positions Kelly had requested.

Several cuts in the budget had to be made by the council when the revenue estimates proposed by Kelly in March were reduced by $4 million.

Kelly had counted on revenues from a state-telephone tax and from state aid to Metro that never materialized.

Earlier this month, Kelly's budget advisers came up with $1.7 million in "unexpected" revenues from federal funds for education and state funds to police and upgraded their estimates on money coming to the county from building permits and licenses. This combined with the budget cuts, provided the council with enough revenues to make the 10-cent tax reduction possible.