Using confidential data from the Internal Revenue Service on who signs a corporation's tax return, we investigate whether the party primarily responsible for the tax compliance function of the firm—the auditor, an external non-auditor, or the internal tax department—is related to the corporation's tax aggressiveness. We report three key findings: (1) firms preparing their own tax returns or hiring a non-auditor claim more aggressive tax positions than firms using their auditor as the tax preparer; (2) auditor-provided tax services are related to tax aggressiveness even after considering tax preparer identity, which supports and extends prior research using tax fees as a proxy for tax planning; and (3) Big 4 tax preparers, in particular, are linked to less tax aggressiveness when they are the auditor than when they are not the auditor. Our findings help policymakers and researchers better understand an important feature of tax compliance intermediaries; particularly, how the dual role via audits is related to observable corporate tax outcomes.

We extend research on the determinants of corporate tax avoidance to include the role of Internal Revenue Service (IRS) monitoring. Our evidence from large samples implies that U.S. public firms undertake less aggressive tax positions when tax enforcement is stricter. Reflecting its first-order economic impact on firms, our coefficient estimates imply that raising the probability of an IRS audit from 19 percent (the 25th percentile in our data) to 37 percent (the 75th percentile) increases their cash effective tax rates, on average, by nearly two percentage points, which amounts to a 7 percent increase in cash effective tax rates. These results are robust to controlling for firm size and time, which determine our primary proxy for IRS enforcement, in different ways; specifying several alternative dependent and test variables; and confronting potential endogeneity with instrumental variables and panel data estimations, among other techniques.