During the first US presidential debate of the 2020 campaign, former vice president Joe Biden pushed his rival President Donald Trump to release his tax returns hours after releasing his own. Responding to questions raised by <i>The</i> <i>New York Times </i>this week that reported the president paid just $750 in federal income taxes in 2016 and 2017, and none in 10 of the previous 15 years, Mr Trump said they would release his records "when they were ready." Mr Biden chimed in, "when? inshallah," using the Arabic word for God willing. While the term is often used sincerely, colloquially it can also be used to indicate something unlikely to happen. Hours before his first head-to-head, the Democratic presidential nominee and his running mate Kamala Harris both released their 2019 tax returns. However, Mr Trump has long kept his personal financial records secret and portrayed himself as a shrewd businessman. Around 40 minutes into Tuesday's debate the issue was brought up with Mr Trump claiming to be paying "millions" in income tax but refusing to detail when he would release his returns. Mr Biden's taxes showed he and his wife Jill paid more than $346,000 in federal taxes and other payments for 2019 on an income of nearly $985,000, before seeking a refund of nearly $47,000 they said they had overpaid the government. "This is a historic level of transparency meant to give the American people faith once again that their leaders will look out for them and not their own bottom lines," said Mr Biden's deputy campaign manager, Kate Bedingfield. "Mr President, release your tax returns or shut up." With more than a million Americans casting early ballots and time running out to change minds or influence the sliver of undecided voters, the stakes are huge as the two White House candidates take the stage five weeks before the November 3 election. Mr Trump arrived in Cleveland for the debate aboard <i>Air Force One</i> and finished a 20-minute preview visit to the venue shortly before Mr Biden landed in the city with some of his top advisers. They were Jake Sullivan, Ron Klain, Mike Donilon and sister Valerie Biden Owens. Mr Biden went directly to the debate pavilion for his own walk-through. Handing in his tax returns before the debate shows that the former vice president is seeking political advantage on an issue that could resonate with voters. Democrats have sought to portray Mr Trump as a tax dodger. The president’s constant refusal to release his returns has been a departure from standard practice for presidential candidates. Trump campaign spokesman Tim Murtaugh responded to Mr Biden's disclosure, by accusing him of being dishonest in public statements about his own past earnings. But Mr Murtaugh did not say whether Mr Trump would release his returns. <i>The Times </i>also reported that Mr Trump was embroiled in a decade-long Internal Revenue Service audit over a $72.9 million tax refund he claimed after declaring large losses. If the IRS rules against him, he could have to pay more than $100m, the newspaper reported. Mr Biden's 2019 return showed most of his income came from a company he said handled payments from his speaking and writing engagements, and from a University of Pennsylvania teaching post from which he took an unpaid leave after launching his candidacy. Ms Harris and her husband, lawyer Doug Emhoff, reported paying about $1.2m in total federal taxes from $3.3m in income for the year, according to their returns. Vice President Mike Pence released a decade of returns before the 2016 election but no tax information since then. Mr Trump and more low-key Mr Biden will debate a range of urgent political challenges, including a pandemic that has killed more than 200,000 people in the US and left millions unemployed. Also on the agenda will be Mr Trump's nomination of conservative Judge Amy Coney Barrett to the Supreme Court, and continued protests for racial justice. Mr Biden, 77, has held a consistent lead over Mr Trump, 74, in national opinion polls, although surveys in the battleground states that will decide the result show a closer contest. The debate will be divided into six parts: the records of the two presidential candidates; the Supreme Court; the pandemic; the economy; election integrity; and "race and violence", which has swept across US cities. A senior Trump campaign official said that the president "knows exactly what he wants to communicate". He said Mr Trump hoped to get into his differences with Mr Biden on trade, "endless wars", the issue of America's "haves and the have-nots" and the Democrat's long career in elected office. Mr Biden is certain to press his criticism of Mr Trump's response to the pandemic and of his efforts to eliminate the Affordable Care Act, the law known as Obamacare, which has helped millions of Americans to obtain health insurance.