In 2016, the Centers for Medicare & Medicaid Services started reimbursing practitioners for their time spent providing advance care planning (ACP) with patients. This study assessed utilization of this policy by examining trends in ACP billing across medical specialties from 2016 to 2021 and differences in ACP service volume by metropolitan status.The authors analyzed Centers for Medicare & Medicaid Services Medicare Provider Utilization and Payment files (2016-2021) from 6 specialty groups using corresponding Healthcare Common Procedure Coding System codes to derive trends in the percentage of practitioners billing any ACP visit. Wilcoxon tests were conducted to compare the average number of visits by metropolitan status.The percentage of practitioners billing ACP visits tripled from 1.76% in 2016 to 4.56% in 2021, with the highest percentage among hospice and palliative medicine practitioners (36.94%) in 2021. ACP service volume was similar by metropolitan status for hospice and palliative medicine, but it was higher in nonmetropolitan regions for cancer-related specialties, non-cancer terminal disease specialties, and primary and geriatrics care.This nationwide analysis showed low adoption of ACP billing by 2021, and it varied widely across specialties. This may reflect practical challenges of ACP related to comfort level with ACP discussion and documentation burden among the professional communities.Despite an overall increase in the proportion of physicians billing ACP codes from 2016 to 2021, adoption remained low. Efforts are needed to address barriers to ACP and provide goal-concordant care to patients.