The D.C. government completed the fiscal year that ended Sept. 30 with a balanced operating budget and $15.3 million left over to help reduce a massive accumulated deficit, according to a financial report recently issued by the District's bond underwriters.

If these projected figures hold up under the scrutiny of a year-end audit, it will mark the fourth consecutive year in which the District has collected far more revenue than it has spent.

It also will further bolster Mayor Marion Barry's claim, to congressional leaders and prospective investors, that the city's once-tattered finances are in good shape.

"Financially, I certainly was impressed by this," said Philip Dearborn, vice president of the Greater Washington Research Center and a specialist on municipal finance. "I had grave concerns about the fiscal 1984 budget being kept in balance and this was a genuine achievement on his Barry's part."

In 1980, at the height of the Barry administration's financial crisis, the city overspent its operating budget by $105 million, boosting the accumulated deficit to $377.8 million.

Although Barry was later criticized for misleading or confusing the public about the precise nature of the budget crisis, he completed the next three fiscal years with sizable surpluses that were dedicated to reducing the deficit.

The city finished up with a $68.3 million surplus in fiscal 1981, a $13 million surplus in fiscal 1982 and a $17 million surplus in fiscal 1983 (which was still $3 million less than Congress had mandated to be set aside that year for deficit retirement).

If the city in fact completed fiscal 1984 with $15.3 million more in revenues than it spent, as the new financial document indicates, then the District's accumulated deficit will have dwindled to $264.1 million.

"That's what we're shooting at," said D.C. Budget Director Betsy Reveal, although she cautioned that nothing is official until the fiscal 1984 audit is completed early next year.

"I think there's no question the four consecutive years of budget balance is a more impressive record than almost any other city has now," Reveal added. "And for our initial entrance into the bond market, it's very important that we continue that track record."

Congress, which for years has been alarmed by the city's accumulated deficit, instructed the city to find $15 million in fiscal 1984 for deficit retirement, which it apparently has done.

During the current fiscal year, the District must set aside an additional $20.1 million to help retire the debt.

The new D.C. financial information was included in a prospectus prepared by Salomon Bros. Inc. of New York City and five other companies that served as the underwriters of $150 million of short-term notes recently marketed by the District.

The District received the highest rating on its notes from Standard & Poor's Corp. and Moody's Investors Service, the nation's two foremost municipal bond rating services.

"The District estimates that the 1984 budget was executed on a balanced basis with an excess of revenues over expenditures and other sources . . . of approximately $15 million," the document states.

The prospectus said that the current budget, for the fiscal year that began Oct. 1, "assumes a continuation of moderate economic growth in the District, increased personal income resulting in part from federal pay increases, and a somewhat higher rate of inflation than experienced in 1984."

City officials now are busy preparing the mayor's fiscal 1986 budget proposals, which will be submitted to the D.C. City Council Feb. 1.

Part of the task will be finding funds to cover a new three-year contract negotiated with 13,000 city workers that will cost the District and the federal government an additional $42 million over the life of the contract.

The city has yet to complete negotiations on new contracts with D.C. police, firefighters and school board employes, which could cost substantially more.