Notwithstanding anything contained in above sec...meaning plse.sir
If a sectin begins with "Notwithstanding....", it means the section overrides the provision of other section or other portion of Act.
Over ride mns sir
Section 37 - Business expenses are allowed as deduction
Section 43B - Nothwithstanding any provision contained in income tax, certain expenses will be allowed as deduction only on payment basis.
So 43B overrrides section 37.