The eldest son of former President Donald Trump has said he did not work on the financial statements at the centre of a civil fraud trial that threatens the family's property empire.
Donald Trump Jr, 45, appeared relaxed in the New York City court as he cracked jokes and denied wrongdoing.
His siblings, Ivanka and Eric Trump, are due to testify in the coming days.
The judge has already found the Trump Organization exaggerated its wealth and falsified business records.
The civil trial will determine what penalty should be imposed. New York Attorney General Letitia James, a Democrat, is seeking a fine of $250m (£204m) and a ban on the former president doing business in his home state.
Donald Trump Jr is the first of the Trump children to give evidence in this case. Earlier this week, he appeared on the conservative Newsmax network to call the trial a "sham" in a "kangaroo court".
He and Eric Trump are co-defendants, alongside their father. The brothers are both executive vice-presidents at the Trump Organization.
Dressed in a blue suit and bright pink tie, Mr Trump Jr testified for a little over an hour. His testimony will resume on Thursday.
The outset of his evidence focused on Generally Accepted Accounting Principles (GAAP) - the standardised practices and guidelines that businesses use to ensure financial records are accurately maintained.
Mr Trump Jr said he was not familiar with GAAP, besides what he could recall from his time studying business at university.
Pressed by state attorney Colleen Faherty on his understanding of the subject, he drew chuckles in court as he responded: "I have no understanding."
"I leave it to my accountants," Mr Trump Jr said.
At another point Mr Trump Jr told the judge he was sorry for speaking too quickly for the court stenographer to keep up.
"I apologise, Your Honour, I moved to Florida, but I kept the New York pace," he joked.
He told the court that he has done "anything and everything" during his time working for the family business. He is not an accountant, however.
Mr Trump Jr testified that his role in the company grew after his father, the Republican president, won the White House.
"We stopped reporting to my father on decisions in the business," he said.
Both Trump brothers became trustees of the company after his father took office in 2017, to avoid conflict-of-interest laws.
When asked on Wednesday whether he had signed off his father's "statement of financial condition", Mr Trump Jr replied: "Not that I can recall."
The afternoon in court proved mostly calm, aside from a few fiery exchanges between Mr Trump's lawyers and the New York attorney general's team near the end of questioning.
Prosecutors pressed Mr Trump Jr on whether he was involved in preparing financial statements for the company.
He said he had relied on others to "put together a document of this nature".
"The accountants worked on it. That's what we paid them for," he said.
Mr Trump Jr told the court the task belonged to longtime finance chief, Allen Weisselberg, who was also charged in this case and pleaded guilty last year to tax crimes.
"I had an obligation to listen to the people with intimate knowledge of those things," he said, adding that he "relied" on Weisselberg and his accounting team.
New York Judge Arthur Engoron, a Democrat, is presiding over the trial and has already found Mr Trump liable for inflating his assets to secure favourable loans.
Hours before his son took the stand, Mr Trump wrote on his Truth Social account: "Leave my children alone, Engoron. You are a disgrace to the legal profession!"
The judge last week fined the former president a total of $15,000 for twice breaching a gag order over comments he made about a court clerk.
Ivanka Trump was initially listed as a co-defendant in the case, before she was removed from the docket and compelled to testify as a witness.
On Wednesday, lawyers for Ms Trump appealed against the order to testify. She is expected to take the stand on 8 November.
The former president, who is the frontrunner to be the Republican presidential nominee in 2024, is himself expected to testify on Monday.
He appeared in court last week to watch the testimony of his former lawyer Michael Cohen, who told the court one of his responsibilities at the Trump Organization was to "reverse engineer" assets to increase their value based on a number "arbitrarily elected" by Mr Trump.
Mr Trump is also facing four criminal prosecutions, including cases in Georgia and Washington DC in which he is accused of seeking to overturn his 2020 election defeat.