Please find the below steps to apply discount after the tax is applied on receipt:
1) eZee POS Back Office>>Configuration>>2) Outlet Operation.
3) and 4) " Edit" the Outlet for which you want to apply the discount after the tax is applied.
5) and 6) Select " Miscellaneous " option and check the drop down for " Discount Type ".
Select the option " Receipt discount after tax ". You may refer below screenshot for the same.