The primary beneficiaries of the tax-limiting measure known as TRIM (Tax Reform Initiative by Marylanders) were supposed to be homeowners. And it was this group, fed up with annual property tax increases from the Prince George's County government, that gave the charter amendment momentum and voted it into law in 1978.

But today, nearly five years after that election, smaller tax bills -- or even frozen tax bills -- are still an elusive goal for many homeowners.

In fact, county budget figures show that a homeowners today are shouldering a greater percentage of the property tax burden than they did in 1978, a trend that was developing anyway and one that TRIM did nothing to stop.

Concerns about the unexpected effects on tax bills and growing worries that cuts have hurt poorer citizens, many of whom do not vote and are most dependent on services, have prompted wide discussion recently of the tax freeze.

From Gov. Harry Hughes and County Executive Parris Glendening on down to the voters, questions are being raised about whether TRIM should soon be reformed, repealed or tightened.

But amid the uncertainties about the future, the major issue remains who has won and who has lost under TRIM.

County budget figures show that what many homeowners expected to happen after 1978 did not: While the increases on homeowner bills have slowed, as a group homeowners have not benefited as much from TRIM as utility companies and apartment owners.

For instance, in the 1984 property tax statements mailed out when the fiscal year began July 1, apartment owners, on average, received lower bills than last year. The owners of single-family homes, on the other hand, received higher ones.

According to budget analysts, homeowners whose property assessments increased 24 percent or more during the last five years -- and that is most of them -- continued to receive higher tax bills despite TRIM.

Budget figures also show that homeowners will pay 67 percent of all county property tax collected this fiscal year, or about $97.1 million of the $143.9 million ceiling set by TRIM. Five years ago, before TRIM went into effect, that same group paid 61 percent of the total, or $88.3 million.

At the same time, apartment owners, who paid $18.4 million in property tax in 1979, are projected to pay less -- about $13.2 million -- this year. Part of that drop could be caused by the conversion of some apartments to nonrental condominiums, budget officials said.

Commercial and industrial properties as a group will pay $30.9 million this year, or slightly more than the $28.5 million such properties brought it in 1979.

"Something is kooky in the process," said TRIM supporter Alvin Kushner, the mayor of College Park and a member of a county task force studying the property tax-burden issue.

There are two reasons for this unexpected outcome of TRIM: the tax freeze amendment itself and the assessment process.

In the first instance, TRIM required that the county limit property tax collections to the $143.9 million it collected in 1979. But while the initiative was designed to provide tax relief for homeowners, all property in the county -- apartment buildings, malls and power stations -- were covered under the limitation.

At the same time, TRIM did not freeze the assessment process, so inflation-spurred assessments continued to rise. Tax Based on Growth Rate

Each year, the state tax assessor's office determines the total value of property and its average rate of growth in the past year for each county in Maryland. Using that average, Prince George's officials calculate a tax rate that, when applied countrywide, will bring in no more money than allowed by TRIM. For example, the year the county assessment went up 6.6 percent, the tax rate was dropped nine cents to absorb the increase.

Thus, the only property owners who received lower tax bills as a result of TRIM were those whose homes decreased in value, remained the same or increased less than 6.6 percent -- the county average. If the value of a home increased more than 6.6 percent, and most of them did, the owner's tax bill increased despite TRIM.

Because homes are bought and sold more often than apartment buildings or power stations, their market value is pushed up more quickly. Home assessments are based exclusively on market value.

Utilities and apartments have a much more complicated system of assessment that considers profit margins and what an investor would pay for them if they were for sale.

This difference in method has led to a generally accepted notion that apartments and commercial properties are "underassessed," that is, the tax assessors cannot accurately gauge their value, and thus underestimate the yearly increases in their value, Apartment owners and the assessors office dispute this view.

But, because the assessor's office shows apartments and commercial property on average increasing in value more slowly than homes, those two groups tend to pull down the county's average annual increase. As a result, more homes fall above that average and pay higher tax bills.

"So it is still the homeowner who is shouldering most of the burden," said Janet Everette, a county budget analyst. "If your concern was to shift the burden off the single-family homeowner, [TRIM] has not solved that problem. It has slowed the rate of growth down for everyone."

A look at tax records at the courthouse in Upper Marlboro illustrates what happened to the county property tax bills of several typical properties: Taxes on a small house in Palmer Park that were $375 in 1979 were $389 in fiscal 1983, an increase of 4 percent; on a Mount Rainier home, taxes in that same period increased from $448 to $484 in fiscal 1973; an increase of 8 percent.

Generally, the more expensive the houses, the bigger the increase. For example, the taxes of the University Park residence of County Executive Glendening and his wife, Frances Ann, increased slightly more than 10 percent since TRIM, from $845 in 1979 to $931 last year.

The increase on Glendening's house, as with the others, resulted from higher assessed values, which in turn reflect inflation. The assessed value of Glendening's house, which is supposed to represent 45 percent of market value, went up 39 percent in the four-year period, from $56,733 in 1979 to $78,688 in 1983.

At the same time the owners of the massive Springhill Lake Apartments in Greenbelt paid $573,581 in county property tax in fiscal 1979, according to tax bills on file in the county tax office. The bill increased slightly the next year but for the three after that the bills showed a sharp decrease. In fiscal 1983, the last bill on file, the complex paid $497,041 in county property tax, a drop of 13 percent since TRIM.

Utility companies' property tax bills all decreased during the first year or two under TRIM but have since increased, according to utility company officials. But the increases have been small and much less than in other jurisdictions.

For example, C&P Telephone's bill went up about $259,000, or slightly more than 5 percent in Price George's between 1979 and 1983. But in Montgomery, its bill shot from nearly $5.1 million to nearly $6.1 million in the same time, a 20 percent increase.

Glendening contends that TRIM provided a windfall of about $26 million to the utility companies, because the tax on non-land property, such as utility company trucks, was tied to the regular property tax rate that TRIM forced the county to cut.

For that reason, the county council recently passed a law that would allow the county to tax this non-land property at a higher rate than residential property.That law is being challenged in court by Potomac Electric Power Co., which contends that it is unconstitutional for the county to separate business property from other property.

TRIM advocates say they are aware that the tax freeze has not stopped tax bills from rising or solved the issue of homeowners picking up most of the property tax tab. But William Goodman, coauthor of the 1978 freeze, said they do not expect to launch a new initiative to deal with these problems.

Instead they say they believe the Pepco court case will establish that they county can levy separate taxes on different kinds of property, as the original drafters of TRIM wanted. This would allow the county, if it chooses, to tax apartment owners and businesses at a higher rate than homeowners.

New money from those sources, coupled with the "fat" they still see in the county budget, will allow Prince George's to survive easily, Goodman said.

County officials, however, are not sure the Pepco court case will get to the issue of different tax rates. They believe the court case will at best provide a small bandage -- $10.5 million annually from the new business property tax -- on a much bigger, long-term problem, the county's future bleak financial data.

Faced with looming budget deficits in the next few years, the Price George's officials are hoping to win more state money and persuade county voters that the property tax freeze must be repealed or substantially modified if the county is to survive.

These dual goals are leading the county toward potentially severe conflicts on both fronts.

At the statehouse, legislators are still fuming about creating a state lottery this year mostly to provide Prince George's with a $7 million "bailout." There is growing sentiment among legislative leaders and Gov. Harry Hughes' staff for state action to ban local tax freezes in Maryland.

Such intervention, it is argued, is needed to protect the school children, nonvoters and poor people who cannot easily get to the county seat of Upper Marlboro to make their opinions known. It would also squelch complaints by other counties that they are being taxed by the state to pay for Prince George's.

"It's unfair to the rest of the state to ask them to subsidize Prince George's County," said Ejner J. Johnson, Hughes' chief of staff, in a comment representative of the feelings of many state officials. "If they want services they're going to have to repeal TRIM. They have a real Hobson's choice -- they can't have it both ways."

In addition, Hughes and legislative leaders worry that too much state help for Prince George's would encourage other local jurisdictions to freeze their property taxes and go, hand outstretched, to Annapolis.

Glendening sees it differently: "We are the largest county in a wealthy state and they are not going to let its major jurisdictional [outside Baltimore City] go down the tubes."

The county may get new state money when several aid formulas for education, police and transportation come up for possible rewriting during the 90-day General Assembly session that begins in January. A similar rewrite three years ago sent millions of new dollars into local government treasuries. But that was an unusually flush time for the state treasury.

At home, where the voters' love affair with the TRIM freeze continues, a state ban on tax limitations would be seen as an end-run around the ballot box, say Prince George's politicians, who nonetheless admit they are enticed by the idea.

Many voters are like Lois and Lindsay Morris, retired Beltsville residents who have lived in the county for 30 years. The Morrises use few county services -- occasionally they borrow library books or take ballroom dancing at the community center -- and have not personally felt the deterioration in the schools, the public works program, the fire department.Their contact with the public schools ended in 1967 when their last child graduated.

The Morrises, who voted for TRIM in 1979, pay less county property tax today than they did before the tax freeze went into effect (Their 1979 tax bill was was $646; in 1983 it was $618, a decrease resulting from an assessment that went up less than the average.) The Morrises believe the tax freeze has helped keep government spending in line and would vote for it again today.

"It just seemed that taxes on the house were going to go so high that it was going to be impossible to meet our obligations," Lois Morris said of her vote in favor of TRIM. Future modification of the freeze might be necessary, she said, "if we can't maintain our services and protect our people. [But] I'm satisfied at this point."

Despite an overwhelming vote last November against loosening the freeze, Glendening is optimistic about the prospects for winning a minor modification in the 1984 elections. He named a task force last week to recommend a ballot question, and modifications are already being prepared by several groups, including public safety unions, which want to exempt police and fire expenditures from the TRIM cap.

The change Glendening is pushing would allow new commercial development to be taxed beyond the $143.9 million TRIM ceiling. It would bring in $5 million to $8 million each year.

Coupled with some state aid and an economic upturn, that would bring in more income-tax and sales-tax dollars and allow the county to survive the next few years, Glendening believes.

Behind these optimistic scenarios there is concern about the future.

"TRIM reflects the mood of the public," said state Sen. Frank J. Komenda, chairman of the county's Senate delegation. Komenda, whose southern Prince George's district is a bastion of TRIM supporters, added, "I'm convinced that if there were a referendum put on the ballot today to repeal TRIM it would fail by a bigger margin than TRIM passed."

Even if the voters approved a change next year, county officials said it would not generate the amount of money needed to overcome many problems. Maintenance and purchase of equipment and repair of roads, deferred over the last few years, will cost millions, as would any effort to address many of the social problems of a school system increasingly filled with disadvantaged children. State Funding Increase Doubtful

In addition, the state has its own money troubles and an imminent increase in state funding to the local governments is far from certain. And the county could lose the Pepco suit and have to return the $10.5 million it has collected -- and put in escrow -- from utilities and other businesses.

Finally, it is likely that county employes -- police officers, firefighters and school teachers -- who this year agreed to forgo cost-of-living increases and saved the county about $20 million, will not be so accommodating next year or the year after.

Leaders of the Prince George's Chamber of Commerce, who say TRIM has been a good marketing tool for attracting business but supported modifications in 1980 and 1982, worry that the freeze, if unmodified, will hurt the county's image and its ability to maintain the roads, curbs, gutters and public buildings business needs.

"The concern is that we were being unrealistic" in TRIM's absolute cap on property tax collections, said Raymond LaPlaca, a Republican developer who is immediate past president of the chamber, and chairman of Glendening's task force on TRIM. "Every new development puts an additional burden on the system -- police, fire, education -- but at the same time the money we're dealing with is worth less.

Public school advocates believe that if present trends continue TRIM could ruin the school system just as the national focus is shifting toward beefing up the public schools. They are concerned that Prince George's may follow in the path of the San Jose, Calif., school system and declare bankruptcy.

While most political leaders are optimistic that at least one escape route will be found, they also say that county taxpayers will never permit a return to the easy budget days of the past, when there was plenty of money to solve nearly any problem and appease any group.

As a result, the future may see fierce competition for limited resources, and that is where the greatest trouble may lie.

"What you're really doing is . . . creating a wedge between rich and poor," said Francis B. Francois, a liberal Democrat who served on the county governing bodies that put in place the 1960s expansion and the TRIM-inspired contraction.

"A place like Bowie will do fine because it can afford the swim clubs. South county will do fine because the poeple there are self-sufficient. And the [less affluent] Inner Beltway will get poorer, with few people wanting to live there.

"If, say the '50s and the '60s were a time of striving for equal opportunity for all, equal services provided by the public for all, then this wil hurt. What this is saying is, the quality of life is what you can afford.