The mechanism of ground and excited state double proton transfer reaction in formic acid dimer has been analyzed with the help of reaction force and the reaction electronic flux. The separation of reaction electronic flux in terms of electronic activity and reactivity, NBO, and dual descriptor lends additional support for the mechanism. Interestingly we found that the ground state double proton transfer mechanism is concerted synchronic, whereas the excited state double proton transfer is concerted asynchronic in nature.