Hedge funds have suffered their biggest margin call since 2020 after Trump's tariffs triggered a sharp drop in global financial marekts. Wall Street banks have asked their hedge fund clients to put up more money as collateral for loans as the value of the assets they hold has slumped, according to three people familiar with the matter. Several big banks issued their biggest margin calls to clients since the start of 2020, underscoring the wild turbulence in global markets on Thursday and Friday. "Interest rates, stocks and oil prices fell dramatically... it was the breadth of the overall volatility that led to the size of margin calls," said a prime brokerage executive. He added that it was reminiscent of the wild swings in markets in the early months following the COVID-19 pandemic. "We are proactively engaging with clients to give them a full understanding of the risks," said a prime brokerage executive at another large US bank.