As Americans scramble to make their year-end charitable contributions, they may have to do so without a key tool for understanding how those charities spend their money: their most recent tax forms.

According to a ProPublica review of public IRS data, which powers our Nonprofit Explorer database, the agency is behind on releasing nearly half a million tax records, known as Form 990s, for tax-exempt organizations. The delays, which began two years ago, are stymying access to key financial information that governments, the public and grantmakers use to evaluate the nation’s tax-exempt companies.

The gap in reporting has become so profound that state charitable enforcement officers are sounding the alarm. In November, the National Association of State Charity Officials sent a letter urging the IRS to address backlogged 990 data releases.