Martin Marietta Corp. said yesterday it has paid an additional $2,565,377 to settle allegations that it overcharged the government for use of a computer facility in Orlando, Fla.

The defense company, which is headquartered in Bethesda, had already paid $898,000 to settle part of the case.

A spokesman for Martin Marietta said the original sum was based on the amount of overcharge that was not in dispute. The additional settlement was agreed to after negotiations between the government and the company.

The inaccurate billing was discovered in September 1986 by the company's subsidiary, Martin Marietta Electronics and Missiles Group. The company disclosed the overcharge to the government at that time.

A subsequent investigation by the Defense Criminal Investigative Service determined that the company had provided inflated cost data, enabling it to receive more money than it was entitled to get.

A Martin Marietta spokesman said the employees involved were disciplined and no longer work for the company. He declined to say whether they were fired or had quit.

In addition, he said the company had tightened its reporting procedures by adding more internal audits and by increasing employee training on billing procedures.

The Justice Department said that under the False Claims Act, companies that cooperate, as Martin Marietta did, are entitled to pay lower fines to settle cases.