We document important interactions between tax incentives and corporate policies using a “quasi natural experiment” provided by a surprise announcement that imposed corporate taxes on a group of Canadian publicly traded firms. The announcement caused a dramatic decrease in value. Prospective tax shields partially offset the losses, adding 4.6% to firm value on average, and vary with the tax status of the marginal investor. Further, firms adjust leverage, payout, cash holdings, and investment in response to changing tax incentives. Overall, the event study and time series evidence supports the view that taxes are important for corporate decision making.