Corporations have increasingly been called on to assume responsibilities for paying fairer shares of tax, while, at the same time, governments have been repeatedly urged to develop more effective corporate tax systems to tackle tax avoidance. Therefore, institutional attributions of tax responsibility for companies seem to have features of both explicit and implicit corporate social responsibility (CSR). However, given that we lack a clear understanding of which form or forms of CSR in relation to tax are expected of companies and (...) how exactly this might be changing, we examine the evolution in institutional expectations of explicit and implicit CSR for corporate taxation. Drawing on a longitudinal content analysis of 992 news media articles from the United Kingdom between 2000 and 2021, we find that institutional expectations of corporate tax responsibility have followed a process of continuous and non-linear hybridization characterized by a pendulum-like trajectory of explicitization followed by implicitization. We discuss the implications of these findings for the theory and practice of corporate tax responsibility and the framework of explicit/implicit CSR. (shrink)