This study presents a mixed-integer linear programming (MILP) model to solve the simultaneous transmission network expansion planning (TNEP) and reactive power planning (RPP) problem. The proposed model considers reactive power, off-nominal bus voltage magnitudes, power losses, multistage expansion, and security constraints. The use of an MILP model guarantees convergence to optimality by using existing classical optimisation methods. In order to validate the approximation performed, the steady-state operation points were compared with those obtained using an AC load flow method. Garver's 6-bus system and a modified IEEE 118-bus system were used to show the precision and efficiency of the methodology. The results indicate that better expansion and generation plans are found by considering RPP simultaneously with the AC TNEP, when the solutions were compared with the plans of the TNEP using the AC model without RPP and the TNEP considering the DC model, with RPP conducted at a subsequent stage. Continuous variables ΔP ij,y,l,t,k , ΔQ ij,y,l,t,k values of the lth block associated with active and reactive power flows in corridor ij, equivalent line y, at stage t, in condition k θ i,t,k voltage phase angle at bus i, at stage t, in condition k f u ij,t,k slack variable of the voltage phase angle calculation equation of corridor ij, at stage t, in condition k f V ij,t,k slack variable of the voltage drop equation of corridor ij, at stage t, in condition k I ij,y,t,k current flow magnitude on equivalent line y, in corridor ij, at stage t, in condition k
