We study the e!ect of licensing-induced, occupation-specific education requirements on workers’ occupational mobility and earnings. We study this question in the context of Certified Public Accountants’ (CPAs) licensing rules, exploiting the staggered intro-duction of a change in the number and composition of CPAs’ educational requirements across states. We find that an increase in mandatory accounting-specific credit hours leads to more time spent in accounting jobs, less cross-occupation job switching, and a reduction in the licensing earnings premium. Supplemental analyses indicate that the e!ects represent a specialization of worker skills rather than a general decline in CPAs’ accounting performance. The collective findings suggest that by imposing occupation-specific course requirements, licensing regimes can create less portable human capital, reducing both occupational mobility and the licensing earnings premium.