We propose a new five-site pair potential for formic acid to be employed in liquid state simulations. The pair potential excellently fits to the MP2/6-31G(d) ab initio dimer potential surface, correctly captures the characteristics of the most important regions of the potential, and locates all seven minima found in ab initio calculations. Both thermodynamical quantities and total radial distribution functions for liquid formic acid were computed employing Monte Carlo simulation techniques. We found excellent agreement between experiment and theory with respect to thermodynamics and structure. The results of the total radial distribution functions exhibit significant improvement compared to the results of the OPLS parameter set.