The far infrared spectrum of HCOOH was recorded at a high resolution (0.0009 cm1)and long path length (72 m) at the far-infrared beamline, Canadian Light Source. Spectrawere recorded in the region 62–300 cm1, showing transitions from the trans-isomer.Ground state rotational transitions with Ka up to 30, were identified up to 175 cm1,extending the observation reported in the literature. A total of 3321 transitions wereassigned and fitted together with previous (4149) published data. An improved set ofrotational parameters was obtained adopting the symmetric top (A) reduction of therotational Hamiltonian in the Ir representation. The newly measured far infraredtransitions allowed the determination of all diagonal and off diagonal 8th orderparameters L and of some of the diagonal 10th order parameters P.& 2012 Elsevier Ltd. All rights reserved.