This study examines a newly introduced DRG system in Indonesia. We use secondary data for 2015 and 2017 from Jaminan Kesehatan Nasional (JKN), a patient level dataset for Indonesia created in 2014 to record public and private hospitals’ claims to the national health insurance system to investigate whether there is an association between changes in tariffs paid and the severity of inpatient activity recorded in hospitals. We find a consistent small, positive and statistically significant correlation between changes in tariffs and changes in concentration of activity, indicating discretionary but limited coding behaviour by hospitals. The results indicate that reducing price differentials may mitigate discretionary coding, but that the benefits of this are limited and need to be compared to the potential risk of having to rebase all prices upwards. © 2021, The Author(s).