Unsure about codes that payers are using for ABA services? This chart outlines the ABA assessment and treatment CPT® codes that have been used for reporting and billing those services. In particular, it shows the conversion of the 2019 Category I and III (temporary) CPT® codes to the 2027 Category I CPT® codes which will take effect on January 1, 2027. The accompanying letter provides additional important information about the 2027 code set.