S. 14A : Disallowance of expenditure – Exempt income -Only those instruments/securities which yielded exempt income during previous year relevant to assessment year would be considered for computing disallowance-If disallowance falls below disallowance under section 14A offered by assessee in return of income, revenue cannot charge tax on income which never was income of assessee chargeable to tax. [S. 139, 143(3), R.8D]