Reviving the Economy Sustainably Towards A Recovery in Twenty-twenty Act or the RESTART Act This bill extends the Paycheck Protection Program, established to support small businesses in response to COVID-19 (i.e., coronavirus disease 2019), for certain businesses, and it establishes a loan program whereby the Small Business Administration (SBA) shall guarantee loan amounts to certain businesses affected by COVID-19. Specifically, the bill provides a paycheck protection loan recipient with 16 weeks to use such funds if the recipient has (1) less than 500 full-time employees, and (2) suffered a decline in revenues of at least 25%. The bill also establishes a loan program whereby the SBA shall guarantee 100% of program loan amounts made to certain small businesses that have not more 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.