How do changes to taxation policy affect the organizational choices of firms? Using historical firm data constructed from Japanese corporate genealogies, we examine the short-run impact of introducing a personal income tax (PIT) in 1887 on tax-motivated incorporation. Between 1880 and 1892, we find that the introduction of PIT increased the share of incorporated firms by more than 3 percentage points, indicating firms chose their organizational structure to avoid new taxation. Furthermore, our results suggest that a corporate income tax may have acted as a backstop to maintain revenue collected through PIT.