In 2020, President Donald Trump and Melania Trump paid no federal income taxes by claiming millions in dubious deductions and carrying over losses from previous years.

Somehow, that’s not the most scandalous detail to emerge following the House’s four-year legal brawl to obtain Mr. Trump’s tax returns. It turns out the Internal Revenue Service did not conduct — let alone complete — mandatory examinations of Mr. Trump’s returns while he was president, despite its own internal policy from 1977 requiring such reviews and the White House’s claims that they were happening. A report by the House Ways and Means Committee, released after members voted Tuesday to make Mr. Trump’s filings public, proposes codifying into law the norm that every president since Richard M. Nixon had observed, until Mr. Trump: the routine release of presidential tax returns.

In April 2019, on the very day the committee inquired about the status of mandatory presidential audits, the IRS notified Mr. Trump that his 2015 return would be examined. But the audit was assigned mainly to one agent, and Mr. Trump threw sand in the gears. The lone IRS employee had to review a return that included over 400 pass-through entities, numerous schedules, foreign tax credits and millions in carried-over losses from previous years.

An accompanying report from the Joint Committee on Taxation, summarizing Mr. Trump’s returns, raises questions about several deductions he’s claimed. For example, he took a $21.1 million deduction in 2015 for donating 158 acres of real estate but had no qualified appraisal for the land. He also reported making cash donations of more than $500,000 in 2018 and 2019 without substantiation, according to the report.

An internal IRS memo said Mr. Trump’s taxes were so complicated that “it is not possible to obtain the resources available to examine all potential issues.” In other words, even if the agency wanted, it lacked the resources for a thorough review. The congressional report recommends that the IRS assign two senior agents, as well as specialists on partnerships, foreign transactions and financial products, to ensure all presidential audits are complete and timely. This is a no-brainer.

Alas, this problem is bigger than Mr. Trump. Former IRS commissioner Charles Rettig has testified the agency lacks the resources to closely scrutinize the filings of many people in Mr. Trump’s stratum. “We get outgunned routinely,” he said. No American should be too big to audit.

Fortunately, the Inflation Reduction Act provided $79 billion for IRS modernization, including expanded resources to wade through complex returns from high-income taxpayers. Paying taxes is a responsibility of citizenship. Taking steps to ensure presidents pay what they owe, by requiring mandatory audits and returning to the norm of releasing presidential returns, would help restore public confidence that tax laws are administered fairly and applied equally.

— The Washington Post