The recent advancements in visible light communication (VLC) will pave the path for high precision, cost-effective, power-efficient, and secure indoor communication networks. The characteristics of VLC make them a potential candidate for the 6th generation of cellular standards, specifically for applications related to short distance and high throughput communication scenarios. However, indoor VLC faces some challenges such as line-of-sight (LoS) link blockages due to obstacles, and uneven power distribution due to unguided non-Line of Sight (NLoS) reflections from the wall which limits its large scale deployment in dense scenarios. In this paper, we have proposed an intelligent reflecting surface (IRS)-aided indoor VLC system with an optimal irradiance angle guided toward the user subject, which can facilitate optimal orientation of the IRS element in order to maximize the received power at the user. Further, we also derive the closed-form expression for the obtained optimal irradiance angle, essentially a cosine of the angle of irradiance for an element of IRS based on the location of IRS and the receiver’s (users) position. In the designing of the irradiance angle, we considered all 4 vertical walls of the room for placing the IRS. In addition, for a given receiver, we have proposed an algorithm to find the optimal orientation of an element of IRS that will produce the maximum power at the receiver. The proposed algorithm returns the rotation angles which will result in the optimal orientation of the element with the time complexity of O(1).