Buried within most of the variants of President Obama’s proposal for extending health care to 47 million uninsured Americans is the notion that tax credits will somehow provide the financing. Tax credits have become popular with politicians in recent years because they look, superficially, revenue neutral. They are not.  A tax credit is money the Treasury never receives, which otherwise would have gone into the government’s general operating fund. If that operating fund could not have underwritten a given subsidy after tax collection, it will experience a budgetary shortfall if it never receives the taxes in the first place.