We examine the heterogeneous effects of copayments of 14 to 21 euros on primary care general practitioner (GP) use in a setting in which access to appointments is based on triage. Using an age-based regression discontinuity (RD) design and variation across areas in whether the copayment is charged (RD-DID), we analyze the effects at the 18th birthday, when previously exempted individuals become subject to copayments. Based on Finnish administrative data from 2011-2019, we find that GP visits decrease by 4-5% in the copayment areas relative to the comparison areas. The reductions are largest for the bottom 20% of the income distribution, i.e., their GP use decreases by 0.08-0.10 annualized visits (7-10%). However, the effects are also larger than average for the top 50%, showing reductions of 0.05-0.06 visits (6-8%).