The Secret Service rented a room at President Trump’s Washington hotel for 137 consecutive nights in 2017 — paying Trump’s company more than $33,000 — so it could guard Treasury Secretary Steven Mnuchin while he lived in one of the hotel’s luxury suites, according to federal documents and people familiar with the arrangement.

Mnuchin, a financier from New York, lived in the Trump International Hotel for several months before moving to a home in Washington. Mnuchin paid for his hotel suite himself, a Treasury Department spokesperson said.

But during his stay, the Secret Service also rented the room next door at taxpayer expense, to screen Mnuchin’s visitors and packages, according to three people familiar with that arrangement who spoke on the condition of anonymity.

For that room, the Trump hotel charged the maximum rate that federal agencies were generally allowed to pay in 2017: $242 per night, according to the billing records. The Secret Service checked in Jan. 25, according to billing records obtained by The Washington Post, and didn’t make its last payment until June 12.

The total bill was $33,154.

The Post has identified dozens of instances where the Secret Service paid money to Trump’s businesses — spending taxpayer dollars, often with little or no disclosure at the time. Often, these payments were triggered by Trump’s own travel to his properties.

This case is different, because it was set in motion by Mnuchin, one of Trump’s top appointees. In 2017, he chose a living arrangement that produced two revenue streams for Trump’s company. One came from Mnuchin. The other came from taxpayers.

In a written statement, a Treasury Department spokesperson confirmed that the Secret Service had rented the room next to Mnuchin’s. The Post asked if Mnuchin had considered that cost to taxpayers, in deciding how long he would stay.

“The Secretary was not aware of what the U.S. Secret Service paid for the adjoining room,” the spokesperson said.

Trump still owns his business but says he has given day-to-day control to his sons Eric Trump and Donald Trump Jr. while he is in the White House. The Trump Organization did not respond to requests for comment, and the White House declined to comment. The Secret Service also declined to comment, saying it would not discuss “the means and methods we utilize to carry out our protective responsibilities.”

The Constitution bars presidents from taking payments from the federal government, beyond their annual salary, now set at $400,000. But Trump — who says he donates his salary — has argued that this provision was not meant to prohibit business transactions such as a hotel-room rental.

Lawsuits challenging this practice have stalled in the federal courts.

Neither the Trump administration nor the Trump Organization has provided an accounting of how much federal agencies have paid to Trump’s company since Inauguration Day in 2017. The Post has sought to compile its own, using documents obtained via public records requests.

The Post has identified more than 170 payments from the Secret Service to Trump properties, totaling more than $620,000. In many cases, the Secret Service was paying to rent hotel rooms at Trump’s properties to accompany the president while he traveled. The actual total is likely to be higher, because the records released so far largely date from 2017 and 2018.

The $33,154 payment to Trump’s D.C. hotel was already known. The Secret Service had not explained why it had spent the money.

But recently, in response to a public records request from The Post, the Secret Service released hotel bills that show the answer: a single, very long stay.

“Arrival Date: 01/25/2017,” reads a five page-long bill from the Trump hotel to the Secret Service, released after a public-records request. “Room Number: 531.”

Room 531 itself is nothing unusual: a standard room with two queen beds, according to a former Trump hotel employee and internal Trump hotel documents obtained by The Post.

But it happens to adjoin one of the hotel’s jewels: the 2,000-square-foot Franklin Suite, with marble bathrooms, a dining table for six and views across to the Environmental Protection Agency building. In recent days, even with the hotel largely empty because of the novel coronavirus pandemic, the Franklin Suite was listed at $8,300 per night.

That was Mnuchin’s suite in 2017, according to one former Trump hotel staffer. The Treasury Department spokesperson said Mnuchin did stay in a suite at the hotel but could not recall the suite’s name. The spokesperson said Mnuchin negotiated a discounted rate with the hotel manager but declined to disclose it.

The Secret Service, which has protected treasury secretaries for decades, took Room 531 to screen packages, visitors and laundry, according to two people familiar with the arrangement, who spoke on the condition of anonymity because of sensitivity about security protocols.

People familiar with Secret Service practices said that was standard procedure when an official stayed in any hotel. During the Clinton administration, for instance, Treasury Secretary Robert Rubin lived in the Jefferson Hotel near the White House for years, and the Secret Service used the room next door, according to news reports.

The difference, in this case, is that Mnuchin and the Secret Service were paying for rooms in a hotel owned by the same president who had appointed Mnuchin.

“Normally, you would deliver any deliveries to the Secret Service and then they would give it to the person under protection,” the former Trump employee said, speaking on the condition of anonymity to stay on good terms with a former employer.

The rate, according to the newly released documents, was $242 per night for every night of the 137-night stay.

The Trump Organization did not respond to questions about how that rate was chosen. One possible reason: For much of 2017, $242 was the maximum amount that federal employees could spend on a hotel room in Washington, according to rules set by the General Services Administration.

That was less than the rates Trump’s company has charged the Secret Service for rooms at his Mar-a-Lago Club in Florida, which have ranged from $396 to $650. That exceeded the maximum government rate, but the Secret Service is permitted to exceed those limits while on protective duty. And the $242 rate was probably less than what Trump’s D.C. hotel might have gotten from a nongovernment customer in Washington. In 2018, for instance, Room 531 rented for as much as $616 per night, according to Trump hotel records obtained by The Post.

But for the Trump hotel it was also a steady rental at a time when only about 42 percent of rooms were occupied, according to previously released data.

“We were not anywhere near full occupancy at the hotel,” the former hotel employee said.

Mnuchin bought a $12.6 million home in Washington in February 2017 and moved out of the Trump hotel sometime in “late spring,” the Treasury Department spokesperson said. The spokesperson did not give an exact date when Mnuchin left the hotel.

For the Secret Service, the last payment on Room 531 was made June 12.

But other payments to the Trump hotel continued: The Post has identified $126,000 in additional payments from the Secret Service to the hotel between January 2017 and February 2018.

The Secret Service has not explained any of the others. But some do seem to follow the pattern from this case, with dollar amounts in multiples of the $242 nightly room rate.

For instance: On June 28, 2017 — a night when Trump visited the hotel for a fundraiser dinner — the Secret Service paid the hotel $33,638.

That is an even bigger payment than the one for Room 531. It is exactly enough to rent 139 rooms at the $242 rate.

But the Secret Service has not said what it was paying for in that case.

Alice Crites and Jonathan O’Connell contributed to this report.