Statutory definitions often carry ambiguous terms and subtle distinctions. However small these distinctions may seem, their interpretation can mean millions in state tax.  In Massachusetts, for example, multistate corporations generally apportion their business income using a three-factor formula based on a property factor, a payroll factor, and a double-weighted sales factor.  However, certain out-of-state corporations, like “manufacturing corporations” or “mutual fund service corporations,” may be required to apportion their business income using Massachusetts’s single-sales factor apportionment formula.  In the event a single-sales factor apportionment formula applies, an out-of-state company’s Massachusetts corporate excise tax liability may increase, as none of that company’s out-of-state property and payroll expenses are accounted for in apportioning income.