MEMBERS OF THE MARYLAND General Assembly, which convenes today, have one advantage over their counterparts in Virginia: they have to raise taxes - but not in an election year. The state's projected deficit of around $120 million cannot be remedied by bookkeeping adjustments or spending cuts, especially since state employees were denied a pay raise last year. Indeed, there will be special pressures to increase appropriations for retirement programs, aid for foster parents and the like, since the state's highest court has just ruled in effect that the governor is not obliged to pay such benefits - even if mandated by law - unless the legislature has provided the funds.

Many state officials, starting with Gov. Marvin Mandel, seem to think that the most palatable way to raise taxes would be to increase the sales tax from four to five per cent. Coincidentally, that would bring in between $110 and $120 million. But while that may be the easiest course, it is not the fairest or most far'sighted one. It would be far more equitable to increase and overhaul the state income tax. That tax now ranges from two to five per cent; but it can hardly be called progressive, because the highest bracket includes everyone with a taxable income over $3000. Del. Benjamin Cardin of Baltimore and his joint committee on tas reform have suggested a number of improvements, including higher personal exemptions and more steeply graduated rates. Besides shifting the tax weight to higher-income groups, some of these proposals would generate more revenue than the sales-tax increase owuld provide. Local governments would also gain, since their own income taxes ride along with the state's tax.

Those revenue gains could be well worth the political heat htat income-tax changes always generate.Besides providing insurance against another budget squeeze in 1978, they could enable state and local officials to do something real about the property-tax increases that are provoking so much public complaint. The steep escalation in real-estate prices and assessments has caused problems for many homeowners and farmers whose incomes are modest and who have no ability or desire to sell their properties. Suburban legislators and gubernatorial aspirants such as Lt. Gov. Blair Lee III seem determined to put a lid on assessment increases.

But merely imposing such controls - if they are constitutional - would force local governments eighte to cut services or to raise property-tax rates. That would obviously defeat the purpose of assessment curbs. The cycle can be broken only by shifting the emphasis from property taxes to a fairly graduated income tax.