According to Johnston, Trump's tax document had turned up in his mailbox.
Maddow said she believed this was the first time Trump's federal tax returns had been obtained by the media. But soon after Maddow's announcement that her show would be covering the returns, the White House pre-empted her with its own Trump tax revelation.
Trump's tax returns have been an area of intense interest since he announced his intention to run for the presidency. Despite decades of precedent, Trump refused to reveal his tax returns, claiming that he was unable to do so because of an audit by the Internal Revenue Service.
Trump, the White House said, had a responsibility "to pay no more tax than legally required."
And in response to the impending report, the White House charged that Maddow is "desperate for ratings."
Here's a statement from a White House spokesperson:
"Before being elected President, Mr. Trump was one of the most successful businessmen in the world with a responsibility to his company, his family and his employees to pay no more tax than legally required. That being said, Mr. Trump paid $38 million dollars even after taking into account large scale depreciation for construction, on an income of more than $150 million dollars, as well as paying tens of millions of dollars in other taxes such as sales and excise taxes and employment taxes and this illegally published return proves just that. Despite this substantial income figure and tax paid, it is totally illegal to steal and publish tax returns. The dishonest media can continue to make this part of their agenda, while the President will focus on his, which includes tax reform that will benefit all Americans."
Disclosure: NBCUniversal is the parent company of MSNBC and CNBC.