How can we enable the option where the IT declarations are approved without proof?

If the you want to enable option where IT declarations are approved without proof after then financial year cutoff date.  

Navigate to the payroll settings, go to Payroll (1)  and click on Settings (2).

In the Pay Groups (3) tab, if you have multiple pay groups configured, select the right paygroup and click on the Configure (4) icon.

In the pay group settings, navigate to the Tax and Deductions (1) section, then select Income Tax (2). To access additional settings, click on the three dots (3) icon.

After clicking on the three dots look for the option which says Approval is required for IT declaration go ahead and uncheck the option to enable approval of declarations.