The D.C. Court of Appeals agreed yesterday to reconsider an April decision by one of its three-judge panels that would have invalidated the city's tax on professionals who work in the city.

On April 20 a three-judge panel ruled that the City Council was barred under the Home Rule Act from imposing the tax because its burden fell mainly on persons who live outside the city.

But since other appeals were possible, the city has continued to collect the tax from self-employment professionals and personal service workers, including lawyers, doctors, architects, artists, writers and accountants.

After the decision by the three-judge panel, lawyers for the city government requested a rehearing by the full nine-member court and yesterday's order granted that hearing. It probably will take place in September.

The full court often takes the opportunity to grant reconsideration in important cases and can overturn or uphold an earlier decision.

In requesting the hearing by the full court, attorneys for the city said that the April decision, if allowed to stand, would impose "a staggering financial burden on the District" and placed "an intolerable cloud on the taxing authoring of the council."

"We submit that the decision . . . is in direct conflict with the holdings of prior local appellate decisions, the plain meaning of the pertinent acts of Congress, the clear expressions of congressional intent and with the spirit of home rule," the city argued.

City officials said the earlier decision could force the city government to refund as much as $45 million in revenue collected since the tax was enacted four years ago.

The appeals court gave no reason for granting the city's request.