Massachusetts, like many states, uses tax credits to attract companies. But also like many states, it struggles to track the effectiveness of these programs. …. For the past half-decade, businesses and legislators in the Bay State have thwarted numerous attempts to track the effectiveness of tax incentives. State Auditor Suzanne Bump has been trying since she took office in 2011 to gain access to business tax returns at the Department of Revenue (DOR) for the purposes of auditing the tax credit programs. Bump is stymied by a state law that bans the auditor from accessing business tax information filed with the department. “Although we are told to audit the tax department, we cannot actually look at tax returns,” she says. “If you can’t look at the source documents, you can’t know how well DOR is executing its functions.” ….