Helping Medicaid Offer Maternity Services Act of 2020 or the Helping MOMS Act of 2020 This bill allows states to provide one year of postpartum coverage under Medicaid and the Children's Health Insurance Program (CHIP). (Current law requires 60 days of postpartum coverage.) The Government Accountability Office must report on information relating to implementation. Additionally, the Medicaid and CHIP Payment and Access Commission must report on specified information relating to coverage of doula services under state Medicaid programs, including coverage barriers and recommendations for improvement. The commission must also report on the use of bundled payments to reimburse providers for Medicaid pregnancy-related services. The bill also eliminates the cap on the total rebate amount for single source and innovator multiple source drugs under the Medicaid Drug Rebate Program beginning on January 1, 2023, and increases the funds available for the Medicaid Improvement Fund for state activities relating to mechanized claims systems beginning in FY2022.