Lara Trump served on the board of a company through which the Trump political operation spent more than $700 million.

Lara Trump, President Trump’s daughter-in-law and a senior campaign adviser, served on the board of a limited liability company through which the Trump political operation has spent more than $700 million since 2019, according to documents reviewed by The New York Times. She was also named on drafts of the company’s incorporation papers.

The arrangement has never been disclosed. One of the other board members and signatories in the draft papers of the L.L.C., American Made Media Consultants, was John Pence, the nephew of Vice President Mike Pence and a senior Trump adviser. The L.L.C. has been criticized for purposefully obscuring the ultimate destination of hundreds of millions of dollars of spending. Ms. Trump is married to Eric Trump, one of the president’s sons.

Ms. Trump was initially intended to be the president of the entity, and Mr. Pence the vice president of it, the documents show.

The president has spent millions of campaign dollars on his own family businesses in the last five years. But the newly disclosed records show an even more intricate intermingling of Mr. Trump’s political and familial interests than was previously known.

A spokesman for the president, Tim Murtaugh, said that neither Ms. Trump nor Mr. Pence were compensated by American Made Media Consultants for their service as board members.

“Lara Trump and John Pence resigned from the A.M.M.C. board in October 2019 to focus solely on their campaign activities. However, there was never any ethical or legal reason why they could not serve on the board in the first place,” he said.

Mr. Murtaugh also said they were not compensated for other positions they were listed as holding.

The documents show that Sean Dollman, the campaign’s chief financial officer, was also the treasurer of A.M.M.C.

By routing large campaign expenditures, such as television and digital ad buys, through an L.L.C., the Trump campaign and its joint committee with the national party, called the Trump Make America Great Again Committee, was able to effectively shield many details of its spending, such as who was being paid and how much.

Other past campaigns, including Mitt Romney’s presidential campaign in 2012, have set up similar structures. The arrangement with A.M.M.C. was part of a Federal Elections Commission complaint over the summer from a watchdog group that accused the Trump campaign of disguising the destination of spending.

The involvement of Mr. Trump’s daughter-in-law is significant, in part because questions have been raised over the last several months about how much money was spent by the campaign and who was aware of it. The first re-election campaign manager, Brad Parscale, was pushed out over the summer and officials who remained on the campaign described a cash crunch.

Mr. Parscale told The Times months ago that he made spending decisions in conjunction with the Trump family.

The president’s son-in-law and senior White House adviser, Jared Kushner, who handpicked Mr. Parscale for the role, positioned himself as the chief executive of Mr. Trump’s re-election endeavor.