In the deep recesses of the bureaucracy, old forms don't die -- they just fade away, slowly.

Take, for example, one of the form letters used when a Social Security administrative law judge rules unfavorably on applications for disability and certain other benefits, an area that has traditionally been treated as one of the agency's most sensitive. In this case, the form has been out of date for almost four years, but still circulates across the nation.

The letters, issued by Social Security hearings and appeals offices around the country, inform the applicants in bold print that the benefit has been denied -- and then tells them that denials can be appealed to the Social Security Appeals Council.

The form contains a warning that unless such an appeal is filed, "you may not obtain a court review of your case." The letter includes a statement that the applicant has 60 days to file the appeal after receiving the notice of denial. The appeal can be filed at a local Social Security office or mailed to the Appeals Council.

For a disabled applicant, totally unable to work (as one must be to receive Social Security disability benefits), a goof-up on mailing can be a tragedy, since the loss of appeal rights can result in the loss of thousands of dollars a year in disability benefits and eligibility for Medicare benefits.

Almost four years ago, the Social Security Administration changed the post office box number to which the appeal must be sent. Before then, the address was P.O. Box 2518, Washington, D.C. 20013.

Since 1984, however, the correct mailing address has been P.O. Box 3200, Arlington, Va., 22203.

But the old form has survived -- a fat, goodly supply -- and many local hearings and appeals offices are still sending out the form with the wrong address to applicants denied benefits.

To enhance the confusion, an official notice in the April 1, 1987, Code of Federal Regulations lists the old Box 2518 as the address of the Bureau of Hearings and Appeals.

The result: hundreds of appeals a month are sent to the wrong address. These include not only appeals forms mailed directly to Box 2518 by applicants, but appeals forms handed in to Social Security local offices and then forwarded by those offices to the incorrect Box 2518 address.

Social Security officials say notices have been sent out repeatedly to the local Social Security offices telling them to get rid of the obsolete form letters, but they still keep going out.

Social Security spokesmen say they know of no one whose appeal to the council has been disqualified because it was received late on account of being sent to Box 2518.

"Twice a week the main post office in the District of Columbia bundles up all the letters addressed to Box 2518 and sends them to the Appeals Council," said deputy press spokesman Phil Gambino.

"As long as the letter is postmarked within the required time, there is no disqualification if it reaches the Appeals Council late because of being transshipped."

Officials estimate that 100 or more letters a week are intercepted by the D.C. post office at Box 2518 and forwarded to the council. The council gets 1,000 to 2,000 appeals weekly, most sent to the correct address, so the misdirected appeals make up 5 percent to 10 percent of the total, officials said.

"We're going to fix the address in the Code of Federal Regulations and we're sending out a new round of notices to local offices telling them not to use the old forms," Gambino said.