The data — printouts from Mr. Trump’s official Internal Revenue Service tax transcripts, with the figures from his federal tax form, the 1040, for the years 1985 to 1994 — represents the fullest and most detailed look to date at the president’s taxes, information he has kept from public view. Though the information does not cover the tax years at the center of an escalating battle between the Trump administration and Congress, it traces the most tumultuous chapter in a long business career — an era of fevered acquisition and spectacular collapse.

The numbers show that in 1985, Mr. Trump reported losses of $46.1 million from his core businesses — largely casinos, hotels and retail space in apartment buildings. They continued to lose money every year, totaling $1.17 billion in losses for the decade.

In fact, year after year, Mr. Trump appears to have lost more money than nearly any other individual American taxpayer, The Times found when it compared his results with detailed information the I.R.S. compiles on an annual sampling of high-income earners. His core business losses in 1990 and 1991 — more than $250 million each year — were more than double those of the nearest taxpayers in the I.R.S. information for those years.

Over all, Mr. Trump lost so much money that he was able to avoid paying income taxes for eight of the 10 years. It is not known whether the I.R.S. later required changes after audits.