Coronavirus Relief Fund Flexibility Act of 2020 This bill allows states to determine how to spend remaining Coronavirus Relief Fund amounts. The bill prohibits funds from being spent on government employee bonuses, lobbying expenses, or budget shortfalls that existed prior to the public health emergency with respect to COVID-19 (i.e., coronavirus disease 2019), while providing a 50% match for funds spent on transportation projects begun in the next year. It requires states to hold 25% of their remaining relief funds in trust for future COVID-19 expenses.