This doesn’t reveal the source, but does provide some insight.
Cut and pasted from the NY Times, 9/28/2020:
The New York Times has obtained tax-return data extending over more than two decades for Mr. Trump and the hundreds of companies that make up his business organization, including detailed information from his first two years in office. It does not include his personal returns for 2018 or 2019. This article offers an overview of The Times’s findings; additional articles will be published in the coming weeks.
The returns are some of the most sought-after, and speculated-about, records in recent memory. In Mr. Trump’s nearly four years in office — and across his endlessly hyped decades in the public eye — journalists, prosecutors, opposition politicians and conspiracists have, with limited success, sought to excavate the enigmas of his finances. By their very nature, the filings will leave many questions unanswered, many questioners unfulfilled. They comprise information that Mr. Trump has disclosed to the I.R.S., not the findings of an independent financial examination. They report that Mr. Trump owns hundreds of millions of dollars in valuable assets, but they do not reveal his true wealth. Nor do they reveal any previously unreported connections to Russia.
THE PRESIDENT’S TAXES
In response to a letter summarizing The Times’s findings, Alan Garten, a lawyer for the Trump Organization, said that “most, if not all, of the facts appear to be inaccurate” and requested the documents on which they were based. After The Times declined to provide the records, in order to protect its sources, Mr. Garten took direct issue only with the amount of taxes Mr. Trump had paid.
“Over the past decade, President Trump has paid tens of millions of dollars in personal taxes to the federal government, including paying millions in personal taxes since announcing his candidacy in 2015,” Mr. Garten said in a statement.
With the term “personal taxes,” however, Mr. Garten appears to be conflating income taxes with other federal taxes Mr. Trump has paid — Social Security, Medicare and taxes for his household employees. Mr. Garten also asserted that some of what the president owed was “paid with tax credits,” a misleading characterization of credits, which reduce a business owner’s income-tax bill as a reward for various activities, like historic preservation.