Provider Relief Fund Improvement Act This bill extends deadlines, expands the uses of, and makes other changes pertaining to the Provider Relief Fund. The fund reimburses health care providers for increased expenses or lost revenue attributable to COVID-19. Specifically, the bill extends the deadline by which providers must use any reimbursements they received in 2020 from the fund to the end of the COVID-19 emergency. Providers must use reimbursements received in the first half of 2021 by the end of the emergency or June 30, 2022, whichever is later. Additionally, the Department of Health and Human Services must distribute the remaining provider relief funds by March 31, 2022. Providers must use these funds by June 30, 2023. The bill also allows the use of the funds for workplace safety activities, such as hiring additional security personnel.