This paper examines Sino-UK financial relations in the fintech sector. Through an empirical focus on fintech payments systems, the analysis locates fintech within broader research on the internationalisation of Chinese finance. Conceptually, the paper responds to calls for more attention to be paid to state actors in fintech development. By examining the relationship between the UK and China in fintech, as part of the UK's wider role in Chinese financial internationalisation, I argue that such a focus on the state needs to be expanded beyond the current focus on domestic policy to include wider questions regarding how fintech sits alongside overseas and international policy concerns. I suggest that one productive way of doing this is to understand fintech as a monetary infrastructure. In so doing, the paper argues that fintech needs to be understood as much as a monetary geography as it is a financial geography.