“A tax code change that impacts how companies account for research and development costs is walloping businesses of all sizes. At best, it is a cash flow challenge, costing large public companies hundreds of millions or billions of dollars, which finance chiefs have said could dent their R&D spending. At worst, business owners wonder if their companies will make it, with some who run small and medium-size firms slowing growth, laying off workers or dipping into personal savings to cover tax bills.”