Loudoun County residents have been spared more than $360,000 in real estate taxes this year under an expanded program for senior citizens and the disabled.

The savings are 88 percent higher than in 1989, before the eligibility requirements were loosened by the county Board of Supervisors. It represents revenue that the county government expected to lose, though at the time Loudoun officials extended the tax savings, few of them foresaw the current economic slump.

"The county didn't have to" make it easier for eligible citizens to get tax breaks, said Catherine V. Ashby, Loudoun Commissioner of the Revenue. "The board chose to."

A year ago, after a change in state law permitted localities to revise tax savings eligibility guidelines, the Loudoun board voted to do so. Before the shift, only applicants with a combined gross income no greater than $22,000 and a net financial worth of no more than $75,000 and who were at least 65 years old or permanently disabled, could receive the tax savings.

Under current rules, seniors and the disabled residents with incomes not exceeding $40,000 and a net worth not exceeding $150,000 can take advantage of the program.

Eligible applicants have two choices: Pay a reduced tax bill or defer the entire bill until the property is sold or the owner dies.

The deferral option has not been popular in Loudoun or in other parts of Virginia, officials said. For the 1989 tax year, 260 county residents eligible for a tax savings chose a reduced tax bill, whereas only four applicants opted to defer the payment. For this tax year, 443 applicants chose a reduced payment, and four asked for deferral.

Virginia officials say the same pattern exists throughout the state, and some other states have had similar experiences.

Property owners opting for reduced bills pay a real estate tax of 2 percent of their gross incomes; the balance of the bill is forgiven permanently. Those choosing deferral pay nothing until the property is sold or the owner dies, Ashby said. When that happens, all deferred taxes, plus interest, must be paid.

The two options are among several tax breaks provided by state and local governments nationwide. Tax analysts generally defend the real estate tax as a fair levy that taxes acquired wealth, but they describe the savings measures as important to protect those whose income does do not keep pace with their property values.

Under the Loudoun program, the applicant's house and up to one acre of the lot on which it sits are eligible for relief. Other lots belonging to the same person are not eligible, Ashby said in a recent report to a County Board committee.

Those seeking tax breaks in Loudoun must list all sources of income and provide information about bank accounts, Ashby said. More than 90 percent of those qualifying for reduced or delayed bills are seniors rather than disabled residents, she said.

Last year's tax bills included information about the program, she said, but because of changes in Loudoun's population, "It's impossible to know how many elderly people out there could qualify," Ashby said.

Less than $6,000 of this year's $362,045 in tax savings is deferred payments; the rest is forgiven. A year ago, the total savings amounted to $192,390.

The increase in the tax break program comes at a time when the county government is contemplating how to deal with a fiscal 1992 revenue shortfall of as much as $28 million, in part attributable to state government cuts and higher local education costs. No discussion of changing the tax relief system has occurred in the supervisors' preliminary budget discussions.