President Donald Trump shows a packaging containing a swab to be used for coronavirus testing during the daily coronavirus task force briefing at the White House in Washington, U.S. on April 19, 2020.

The Republican National Committee is catching up on its payments to legal advisors on the president's impeachment defense team.

Kasowitz, Benson and Torres, a firm founded by longtime Trump legal advisor Marc Kasowitz, was paid $20,000 by the RNC in March for "legal and compliance services," according to a new Federal Election Commission filing reviewed by CNBC. An RNC official confirmed the payment was for the work the firm did for Trump in the congressional battle over whether the president should be impeached.

This would mark the first time the firm has been paid by the RNC, records show, although it has received checks from President Donald Trump's campaign in the past.

Trump hired a partner at the firm, Eric Herschmann, in January to assist Trump's legal defense team against Democrats pushing for impeachment. He was a vocal defender of the president's when the time came to speak in front of the U.S. Senate after the House impeached Trump.

"The case against President Obama would have been far stronger than the allegations against President Trump," Herschmann said at the time. He was referring to a discussion Obama held with Russian President Dmitry Medvedev over a missile defense system. Later, the lawyer attacked Biden and his son Hunter for the work the younger Biden did the board of a Ukrainian energy company. Neither Obama nor Joe Biden were found to have engaged in wrongdoing.

Trump was acquitted by the Senate earlier this year after the House impeached him for actions related to a controversial call with Ukrainian president Volodymyr Zelenskiy. Trump asked then the new president of Ukraine to look into Hunter Biden's role on the energy company's board, and his administration withheld military aid to the country shortly after that conversation.

Democrats accused Trump of using his office for his own political gain, which the president denied.

A spokesperson for the Kasowitz firm did not return a request for comment.

The RNC previously has spent money on legal costs that went to Trump allies.

As the Washington Post reported in January, the RNC paid Trump lawyers Jay Sekulow and Jane Raskin $225,000 through November. These payments only represent a fraction of the millions the RNC and Trump-related entities have spent on legal matters, with some related to the House impeachment inquiry and others linked to the investigation into Russian interference by special counsel Robert Mueller.

Kasowitz has been close to Trump for years and first advised him as president during the early stages of investigation into Russian interference. Kasowitz specifically took on former FBI director James Comey in 2017 for his claims that Trump asked for his loyalty after the head of the bureau spoke in front of Congress. Trump fired Comey in May of that year.

A year later, the campaign paid the Kasowitz firm over $320,000 for "legal consulting."