Introduction On January 19, 2021, the IRS published guidance in Notice 2021-10, extending critical deadlines and rules relating to investments in qualified opportunity zones. First, any investors facing a deadline between April 1, 2020, and March 31, 2021, to invest their qualified capital gains in a qualified opportunity fund (“QOF”) now have until March 31, 2021, to invest those gains. Second, for purposes of the “substantial improvement,” requirement whereby QOFs or Qualified Opportunity Zone Businesses (“QOZB”s) must “double the basis” of property within any 30-month period in order for it to be qualified opportunity zone business property (“QOZBP”), the entire period from April 1, 2020 to March 31, 2021, is disregarded – the 30-month improved period is tolled during that period. Third, All QOFs having a testing date between April 1, 2020, through June 30, 2021, for the requirement that 90% of its assets be invested in qualified opportunity zone property, and fail the test, will automatically be granted “reasonable cause” relief from the failure. Although not explicitly stated, we expect that the failure to meet the 90% test on these dates will also be disregarded for purposes of determining whether the QOF meets the opportunity zone requirements for any tax year. In addition, the Notice allows an additional 12 months on top of the original 12-month period that a QOF has to reinvest proceeds from a sale of property by the QOF or the return of capital to the QOF, if any of the original reinvestment period includes June 30, 2020. Finally, the Notice allows up to an additional 24 months to spend funds intended to be covered by a working capital safe harbor by June 30, 2021, extending the safe harbor period to up to 55 months (up to 86 months for start-up businesses).