The U.S. Department of Defense owns more than half a million properties worth in excess of $800 billion dollars. The military’s real estate holdings span the globe and, all together, sprawl across 30 million acres.

Pentagon auditors can’t explain what half the properties are for—and doesn’t have a plan for finding out. All this according to a Sept. 8 report from the Government Accountability Office.

The nearly trillion-dollar real estate glut is merely another example of egregious military waste.

Way back in 1997, the GAO identified the Pentagon’s real estate record-keeping as a “high risk” problem. The Defense Department could sell unused facilities and save billions.

It just needed to figure out exactly what buildings it owned and how it used them all. But military bureaucrats made only passing attempts to find out. The Defense Department is probably still sitting on billions of dollars’ worth of properties it has no use for, despite 17 years of GAO goading.

“We found in September 2011 that DoD was limited in its ability to reduce excess inventory because DoD did not maintain accurate and complete data regarding the utilization of its facilities,” the GAO states in its new report.

The Pentagon won’t sell off facilities because it has no idea what’s going on in many of them. Nobody’s keeping good, centralized records. Individual property managers aren’t performing mandatory audits—and the Pentagon isn’t holding them accountable.

The Office of the Secretary of Defense is in charge of the Pentagon’s real estate. It uses software called the Real Property Assets Database to keep track of land and buildings.

In theory. In practice, the GAO found that the software “showed facility utilization data for less than half of DoD’s total inventory, and these data often were incomplete or did not reflect the true usage rate of the facilities.”

The GAO sent investigators to 11 random facilities—representing all four branches of the military—in order to compare actual facilities to the Pentagon’s database. The inspections didn’t go well.

For starters, the Army has developed its own software to checks for errors in the Pentagon’s real estate database—basically, the Army program takes the land and buildings the ground combat branch knows it has and compares them to what the Defense Department says the Army has.

During the GAO’s visit with the Army, officials from the ground combat branch showed off the program. The investigators told the officials which buildings they planned to inspect. The Army representatives booted up their software and plugged in one of the addresses.

The program found 45,000 inconsistencies. That is to say, compared to the actual property in question, the military’s main listing for this one address was off by tens of thousands of small details. Now multiply that by half a million addresses and it becomes clear how befuddled the Pentagon is.

The Army also provided the GAO access to the Army’s own internal real estate database. Investigators noted that the Army’s database claimed that service officials reviewed facilities in the years 0012, 1776, 2201 and 3013. The Army promised to fix the error.

Visits to Navy and the Air Force facilities revealed similar problems. Investigators found abandoned buildings that the two branches reported as still being in use. The GAO inspectors discovered that the Navy and Air Force had demolished buildings without ever reporting them to the Pentagon. The investigators found entire building complexes that the branches reported as single structures.

The whole military real estate system is a mess. Defense Department directives mandate that on-site facility managers audit their own buildings every five years. Investigators found that, in truth, this was only happening around 20 percent of the time.

The military has taken a few steps to improve the situation, but it’s all too little, too late. All of the Pentagon’s efforts have modestly boosted the overall occupancy rate for its half a million structures from 46 percent four years ago to 53 percent today.

That means the military still has twice as much real estate as it actually uses.

The GAO report includes comments from the Pentagon. The military concurs with the report and promises to do better.

Don’t count on it. The GAO “found that DoD’s plans to eliminate excess facilities in the future were unclear,” and that the Pentagon “had not defined the strategies and measures it intended to employ to eliminate excess facilities on its installations.”

So there’s no plan. Billions of dollars in unused or underused property just sit around costing taxpayers money. Worse, the people who are supposed to be monitoring the sites just aren’t doing their jobs.