Reviving the Economy Sustainably Towards A Recovery in Twenty-twenty Act or the RESTART Act This bill establishes a loan program whereby the Small Business Administration (SBA) shall guarantee loan amounts to certain businesses affected by COVID-19 (i.e., coronavirus disease 2019). Specifically, the bill requires the SBA to guarantee 100% of program loan amounts made to certain small businesses that have not more than than 5,000 full-time employees. The terms for such loans shall include (1) a maximum duration of not more than seven years; (2) an amount that is not greater than 45% of 2019 gross receipts, up to $12 million; and (3) no payment on principal for the first two years of the loan. A lender that is otherwise approved to make paycheck protection loans may make and approve loans established by the bill, and a recipient may use loan funds for specified allowable expenses including payroll costs, rent, utilities, and personal protective equipment. Such loans may be forgiven up to the amount of total losses incurred by the recipient in the taxable year 2020.