The Treasury Department needs to build more search functionality into its online government spending database and do a better job highlighting what data might be inaccurate, according to a congressional watchdog.

The department must do more to secure the site and comply with federal open data policies, the Government Accountability Office said in a report published Thursday.

Treasury is mandated by Congress to report quarterly agency expenditures on USASpending.gov, which offers the public a detailed breakdown of the more than $4 trillion the government spends every year. While publishing spending data promotes government transparency and oversight, auditors found the site lacks a number of features that would give citizens greater insight into how taxpayer dollars are being spent.

The site doesn’t provide structured, machine-readable metadata on agency contracts and obligations, going against recommendations from the Office of Management and Budget, the report said.

“Without easy access to information that fully describes the data, it may be difficult or time-consuming for users of USAspending.gov to find the information available on other websites, and determine whether or how to use the data for their purposes,” auditors wrote. They added the site doesn’t allow users to filter contracts by program source or city, violating the Federal Funding Accountability and Transparency Act of 2006.

A sizable chunk of the data on USASpending is also of questionable quality, and while the onus for reporting accurate information falls on individual agencies, Treasury doesn’t completely disclose data quality issues on the site, the report said.

Last year, GAO reported less than 1 percent of reported grants, contracts and loans were fully consistent with agencies’ internal records. Treasury officials also told GAO inconsistent information or lack of reporting limit their ability to publish some categories of data on the site, but auditors found those issues aren’t publicly stated.

“As a result, the [site] does not consistently provide a clear and complete presentation of federal spending,” they said. “Because Treasury does not disclose these limitations, it could limit the ability of taxpayers and policymakers to fully track federal spending with this tool.”

Some download links on the site were also unsecure or tied to nongovernment websites, auditors said, which pointed to shortfalls in the agency’s security vetting process. Treasury officials have already taken steps to address these issues, they said.