Optimal tax systems with endogenous behavioral biases

•We consider the implications of a tax systems perspective for behavioral public finance.•We use two simple examples to illustrate the value of integrating these two strands of the literature.•Biases are endogenous to policy: just as there is an optimal ETI, so too are there “optimal biases”.•Endogenous biases can alter the optimal choice of non-rate policies like the size of the tax base.