In today's time, we use Leave Application System managed by some central authority. This can lead to corruption, misuse by a single authority or unnecessary time for approval. So, in this paper, we have developed smart contract architecture for Leave Management System using Solidity and Ethereum, which is a decentralized app architecture leveraged from Blockchain Technology. We also include smartphones as IoT devices by which any client can use this app. Due to the resource-constrained nature of these devices, the smart contract app is coupled with an alternative centralized architecture which is a classic client/server architecture with an underlying Blockchain backend. © 2019 IEEE.