inflation & other indexes cahnge on a daily basis. There is a need to change the rates of tax, concession granted wtc. wit hthe changing demands of the economy various tax reliefs are designed.. hence it is necessary to upgrade it...
The fast changes in economy demand timely suitable changes in tax structure also. Various decisions pronounced by high courts and Supreme court in Income tax from time to time are also taken into account by govt. to effect amendments wherever necesary in the best interest of revenue.
Simply,Without any amendment there is not any possibility of Growth. Similarly,Income tax is Amended to do better in any field like in Collection,Tax Evasion area,,etc.