ANNAPOLIS -- It is being advertised as a model of fairness with a bottom line that Maryland taxpayers can appreciate: lower tax bills for many, better roads and schools for everyone.

But as members of a special state commission begin marketing the $1 billion tax plan they unveiled last week, the actual effect remains uncertain. Whether an individual will receive a tax break or a tax increase hinges on decisions far removed from debate over the proposal itself, decisions as varied as buying a boat and quitting smoking.

Although the plan is touted as providing strict accountability for the new revenue extracted from Marylanders, about one-third of the money would be funneled to state and local governments with no strings attached, its use dependent on the priorities of officials across the state.

Additionally, changes to the state's income tax system would produce far more than the $100 million talked about by commission members. The changes would raise more than $230 million from the top one-third of Maryland taxpayers -- much of it from higher-income families in the Washington suburbs -- while cutting about $125 million from the income tax bills of families with adjusted gross incomes of less than $40,000.

Indeed, although members of the Maryland Commission on State Taxes and Tax Structure characterize their proposal as reform that will lower the average Marylander's overall tax burden, that is at best an educated guess, commission staff members acknowledge.

The actual impact will depend on lifestyle and consumption choices.

The effect of planned property tax relief and income tax reductions for a middle-class family, for example, could be more than wiped out by the purchase of a new car or boat, which, under the proposal, would be subject to a new annual levy based on value, plus a higher sales tax.

Sen. Laurence Levitan (D-Montgomery), chairman of the Senate Budget and Taxation Committee, said he was skeptical of the proposal's promotion as tax relief.

"It's tough to figure out how you get tax equity and raise $800 million," said Levitan, who has emerged as a leading critic of the plan. "Most people will end up paying more."

In evaluating the complicated plan's effect on different income groups, "we had to do a lot of guessing," conceded Philip M. Dearborn, the commission's executive director. "We can say that certainly a lot of low-income people will come out with a tax reduction" under the plan, he said. "To quantify beyond that is just statistically not possible."

Along with restructuring income tax rates, the plan would raise the state sales tax from a nickel to 5.5 cents on the dollar, expand it to cover many new services and goods, and impose a new 2 percent personal property tax on cars and boats.

The resulting revenue, about $1.1 billion, would be distributed through a combination of income tax cuts for the poor and the lower middle class; about $180 million in property tax relief; $330 million in new school funding, weighted toward Baltimore and poorer rural counties; and $187 million for county transportation projects. About $335 million would be spent on general county and state government operations.

As Gov. William Donald Schaefer and state legislators begin reviewing the plan, at center stage will be the question of whether its broad social goals supersede public unrest over taxes. Schaefer has endorsed in principle the recommendations of the panel, which he appointed three years ago, but has not decided which specific ideas to forward to the General Assembly when it convenes next month.

In releasing the report, panel Chairman R. Robert Linowes, a Montgomery County lawyer, said the group had been successful in its mission of making the state's overall tax system fairer and bolstering the poorest local governments.

Its recommendations also sought to give every county a stake in the outcome, calling for enough new revenue so that even wealthy areas such as Montgomery County would receive additional money. Although the additional $12 million Montgomery County's government would receive is dwarfed by Baltimore's $150 million share, Linowes and other commission members argue that the plan, taken as a whole, is equitable and socially desirable. Ignoring problems in the Baltimore schools or on the Eastern Shore, they say, will eventually damage the state's overall economic competitiveness, to the detriment of every jurisdiction.

The details, however, are a different story, and lobbyists and legislators are focusing attention on specific parts of the plan they regard as unfair.

Del. Gene W. Counihan (D-Montgomery), for example, estimated that taxpayers in Montgomery will pay as much as $150 million more in new taxes -- by far the most of any jurisdiction -- "and effectively get nothing back." Statistics from the state's income tax division for 1989 show that almost a quarter of the residents who would pay higher income taxes under the Linowes plan live in Montgomery, and a majority live in the Washington region.

"This is a little bit too big of a bite coming off the election," said Robert R. Neall, a former Republican legislator recently elected Anne Arundel County executive. Given the wealth of Anne Arundel residents, Neall said, the county "will be a giver, not a taker" under the tax plan.

The reaction of county leaders such as Neall will be crucial to the future of the Linowes panel's tax proposals. While plenty of business and consumer lobbyists are likely to oppose the plan, potential support will be concentrated among those most likely to benefit: Baltimore and its local civic and business boosters, teachers, highway construction contractors and county government leaders.

Business lobbyists also are taking aim at the sales tax, saying it is the wrong time to hit consumers in the pocketbook. Although Linowes has argued that many of the new services to be taxed are mostly used by business or the wealthy, such as window washing and tanning salons, the recommendations also would extend the higher sales tax to contemporary staples such as cable television.

"It is just going to increase the cost, and that is something that is going to be passed on to the consumer at a time when people are trying to hold taxes down," said lobbyist Bruce C. Bereano, who represents three industries that would be hit by the new taxes: tobacco, cable television and car leasing.

Other questions remain. Though the Linowes plan provides $182 million for counties to lower property tax rates, maintaining those lower rates beyond a year is a decision left to local officials. In addition, the commission skirted politically sensitive questions involving whether the state should maintain its host of expensive income tax and sales tax exemptions, including a 40 percent capital gains exclusion that costs an estimated $50 million annually. The panel recommended that legislators review those tax provisions at their leisure, an approach some lawmakers said they intend to adopt for the entire package.

"What we have to do is convince our constituents that, overall, taxes are going to drop," said Sylvania W. Woods Jr. (D-Prince George's), chairman of the county's House delegation. Prince George's could prove a powerful swing vote in the tax debate; the county would receive the second-highest amount of aid, but it is also home to thousands who would pay more.

"They are going to be upset about it and not going to buy it," Woods said of taxpayers. "If we spend the next year convincing them, we would be in better shape."