Electrically tunable optical properties have been demonstrated in many solid-state materials such as semiconductors, transparent conductive oxides and graphene. However, their tunability is limited in the visible range due to the requirement of extremely large charge build-up or high capacitive fields. Here, we propose strongly correlated materials for circumventing such limitations. 1T-TaS2, a strongly correlated material exhibiting charge density order at room temperature, allows tuning of its optical properties with an in-plane electrical bias. The electrical bias causes the charge density waves to slide and thereby alter their coherence and condensation. As a result, the optical conductivity or dielectric function of this layered material changes with an in-plane bias. Here, we report measured anisotropic dielectric functions of mechanically exfoliated thin films of 1T-TaS2 and their electrical tunability. We observe a maximum refractive index change on the order of 0.1 in the visible range with DC and AC in-plane biases.