When one prepares P&L a/c one has to follow a set format. In this format sales less expenses leads to profit after profit is arrived at one pays income tax on profits! So how can one deduct income tax as an expense?
Are you trying to teach that in the equation you cited Tax has now qualified as "expense" ??? let me suggest you should read an ILO ready reckoner "How to read a balance sheet ".Your concepts will straighten out in less than an hour!