The COVID-19 pandemic led to an abrupt increase in the number of individuals engaged in day trading in Brazil, reaching around 100,000 active participants per day. Using data on all transactions carried out on the Brazilian stock exchange, we document gross losses of R$9.9 billion between the onset of the pandemic and December 2023—equivalent to an average loss of R$10,200 per individual. Our results highlight the systematically unfavorable nature of day trading for individual investors, constituting a persistent mechanism for the transfer of wealth from individuals to financial institutions. This pattern proved particularly harmful during the pandemic, when hundreds of thousands of new entrants, in search of an extra source of income, joined the market and thereby accelerated the pace of losses.