waderoush writes "Engineers and hackers don't think much about tax policy, but there's a bizarre development in California that they should know about, since it could reduce the pool of angel-investment money available for tech startups. Under a tax break available since the 1990s, startup founders and other investors in California were allowed to exclude or defer their gains when they sold stock in California-based small businesses. Last year, a California appeals court ruled that the tax break was unconstitutional, since it discriminated against investors in out-of-state companies. Now the Franchise Tax Board, California's version of the IRS, has issued a notice saying how it intends to implement the ruling — and it's a doozie. Not only is the tax break gone, but anyone who claimed an exclusion or deferral on the sale of small-business stock since 2008 is about to get a big retroactive tax bill. Investors, entrepreneurs, and even the plaintiffs in the original lawsuit are up in arms about the FTB's notice, saying that it goes beyond the court's intent and that it will drive investors out of the state. This Xconomy article takes an in-depth look at the history of the court case, the FTB's ruling, and the reaction in the technology and investing communities."