A density functional calculation is performed to analyze the tetracyanoquinodimethane (TCNQ)/Au(111) interface, includ-ing the effect of the molecular charging energy on the transport gap. We find that the adsorbed TCNQ molecules are bent so that the edge N atoms are closer to the Au(111) surface. Theoretical scanning tunneling microscopy (STM) imaging is carried out and compared with the experimental STM for the TCNQ/Au(111) self-assembled structure, finding good agreement, and validating the interface geometry obtained in our calculations. We show that the alignment between the metal and the organic levels is controlled by the charge transfer between the two materials and the dipole created in the molecule because of its deformation when adsorbed in Au(111). The calculated trans-port gap is 3.1 eV.