The Trump administration’s proposed tax reform plan to spur economic growth would lower the corporate tax rate to 15% from 35% and offer U.S. companies a one-time “tax holiday” rate of as low as 10% to bring home the stockpile of cash earned overseas. Given that the offshore stash is believed to total more than $2 trillion, advocates for a tax holiday claim that this influx will encourage companies to invest in their businesses, creating millions of new jobs. Skeptics expect companies to use much of the cash to repurchase their shares, just as they did in response to the tax holiday the Bush administration provided in 2004. Politicians across the political spectrum, corporate executives, and media commentators blame share buybacks for job losses, stagnant wages, and underinvestment in businesses. So if the tax holiday comes to pass, what should companies do? They should follow a golden rule: Buy back shares only when they are meaningfully undervalued and no better opportunities to invest in the business exist.