Disabled Access Credit Expansion Act of 2021 This bill modifies the tax credit allowed to eligible small businesses for expenditures to provide access to disabled individuals to increase (1) the maximum allowable amount of such credit to $20,500, and (2) the limitation on the gross receipts of such businesses to $2.5 million for purposes of determining eligibility for the credit. The bill directs the Department of Justice (DOD) to carry out an ADA (Americans with Disabilities Act) Mediation Program to facilitate voluntary mediation to resolve disputes arising under the ADA and to provide training for mediators. DOD must report to Congress on its ADA Information Line (a toll-free line to provide information and materials to the public about ADA requirements).