This study empirically analyzes the association between the degree of tax credit (‘DTC’ hereafter), defined originally considering the alternative minimum tax, and possibilities for tax investigation (‘PTI’ hereafter) and that between DTC and the imposed amount by the result of tax investigation (‘ATI’ hereafter). Under information asymmetry between the tax authority and firms, it can be expected that firms’ plausible effort to reduce tax burden through disqualified tax credits will increase PTI. Based on the regression with the Probit and the Tobit model using a sample panel of randomly selected 201 firms, this study found following empirical results. DTC significantly increased PTI, which implies that DTC is highly likely to be an unknown criterion the tax authority adopts, and that the tax authority deems high DTC to be a signal of tax evasion. However, DTC did not significantly affect ATI, which implies that, contrary to suspicion of the tax authority, firms do not make an extra effort to reduce tax burden through tax credits. In all, this study shows that, despite the function to help achieve various policy goals by reducing tax burden, tax credits can have a contradictory effect on firms via unfoundedly increasing PTI, and, as a result, the tax authority should devise more rational and elaborate schemes to select tax investigation targets.