A new fundamental equation of state is presented for trans-1-chloro-3,3,3-trifluoro-1-propene [R-1233zd(E)]. Due to its preferable thermophysical properties and non-flammability, this fluid is considered as one possible alternative for 1,1,1,3,3-pentafluoropropane (R-245fa). The new equation is valid for temperatures from 215 K to 444 K and pressures up to 35 MPa. Typical uncertainties in calculated properties in this range are 0.01 % in liquid densities, 0.04 % in vapor densities, 0.04 % in vapor pressures, and 0.12 % in vapor- and liquid-phase sound speeds. Improvements from the previous equation (Mondejar et al., 2015) include an upper limit increase in pressure to 35 MPa and decreased uncertainties in liquid-phase sound speeds. The equation shows quite reasonable extrapolation behavior at extremely low temperatures, and at very high temperatures and pressures. The ISO/TC86/SC8 committee has agreed to recommend this equation as an international standard formulation for R-1233zd(E).