143 (1)(b)

section 143(1) where a return has been filed u/s 139 or in response to notice u/s 142(1) calling for further details of return, ... such return shall be processed after considering:
sec 143(1)(a). (i)any arithmetical error;
(ii)any incorrect claim;
(iii)disallowance of loss if return of proceeding year is furnished beyond time u/s 139, or (iv)disallowance of any deduction or
(v) disallowance of any expenditure or
(vi) addition of income appearing in Form 26AS or Form 16A or Form 16 which has not been included in computing the total income in the return

section 143(1)(b) refers to computation of tax and interest, if any on the basis of the total income computed after taking into consideration of the above mentioned adjustments u/s 143(1)(a)

Section 143(1) explains the scheme for PROCESSING OF RETURNS Filed u/s 139 i.e Regular Returns or Return u/s 142(1) i.e. when AO asks to file the Return. It Suggests that total Income shall be computed after following Adjustments:

- Any Arithmetical Errors

- Any Incorrect Claim made in the Return

- Disallowance of:
* Loss to be c/f if return is filed late
* Expenditure claimed in excess
* Deductions u/s 10AA & 80IA series if return is filed late.

- Addition of Income if shown in 26AS/Form 16/ Form 16A which has not been taken into return.

These Adjustments have been explained u/s 143(1)(a).

While Section 143(1)(b) tells; Whenever any adjustments is being made u/s 143(1)(a) then All Tax, Interest etc shall be computed on amount which has arrived u/s 143(1)(a) i.e after the above adjustment.

Whenever demand is raised u/s 143(1) then it is raised u/s 143(1)(b) only.

Thanks, Be Helpful to One Another.

nitesh sir your explain always good