Large contracted correlation consistent Guassian basis sets were used in electronic structure calculations for the HFCO --> HF + CO unimolecular reaction at 3855 different geometries. Two types of analytical functions were then used to fit these energies. One is the polynomial expansion using Simons-Parr-Finlan coordinates (at the fifth or sixth order), the other is the many-body expansion. The residual standard deviations of the fits for these three surface’s are 1.1, 0.4, and 1.5 kcal/mol, respectively. The zero-point corrected barrier heights for these three surfaces are 44.5, 44.4, and 45.7 kcal/mol, respectively, compared to experimental estimates in the range 43-49 kcal/mol. The geometries and harmonic frequencies of HFCO and the transition state are compared with other ab initio and experimental estimates.