(a)if income has been assessed for the first time,—(i)where return has been furnished, the difference between the amount of income assessed and the amount of income determined under section 270(1)(a);(ii)where no return of income has been furnished or where return has been furnished for the first time under section 280,—(A)the amount of income assessed, in the case of a company, firm or local authority; and(B)the difference between the amount of income assessed and the maximum amount not chargeable to tax, in a case not covered in item (A);