This paper studies whether and how policies that promote a currency’s use in trade invoicing can also strengthen its role as an anchor currency in other economies’ exchange rate baskets. We exploit the establishment of RMB swap lines by the People’s Bank of China as a natural setting to examine this mechanism. We first estimate countries’ implicit currency baskets and the weights assigned to the RMB, and then use a staggered difference-in-differences design to assess the effect of initiating swap line agreements on the RMB’s weights in these baskets. Our results indicate that RMB weights increase by approximately 5% about nine months after a swap line is introduced and remain persistently higher thereafter. Finally, we develop a three-country DSGE model to interpret these findings, showing that by promoting RMB invoicing, swap lines reinforce the RMB’s role as an anchor currency for exchange rate stabilization.