Against the general belief that carbonic acid is too unstable for synthesis, it was possible to synthesize the solidas well as gas-phase carbonic acid.It was suggested that solid carbonic acid might exist in Earth's upper troposphere and in the harsh environments of other solar bodies,where it undergoes a cycle of synthesis, decomposition, and dimerization.To provide spectroscopic data for probing the existence of extraterrestrial carbonic acid,matrix-isolation infrared (MI-IR) spectroscopy has shown to be essential.However, early assignments within the harmonic approximation using scaling factors impeded a full interpretation of the rather complex MI-IR spectrum of H2CO3. Recently, carbonic acid was detected in the Galactic center molecular cloud and triggered new interest in the anharmonic spectrum.In this regard, we substantially reassign our Argon MI-IR spectra relying on accurate anharmonic calculations. We calculate a four-mode potential energy surface (PES) at the explicitly correlated coupled-cluster theory using up to triple-zeta basis sets, i.e., CCSD(T)-F12/cc-pVTZ-F12. On this PES, we perform vibrational self-consistent field and configuration interaction (VSCF/VCI) calculations to obtain accurate vibrational transition frequencies and resonance analysis of the fundamentals, first overtones, and combination bands.