Hi Rahul,
/Qxx wage types are only generated when wage type is marked as taxable but not taxed under processing class 69 or if wage type has processing class 71 marked to specification which when looked into taxability model table T5UTM under tax class has combo which has tax types in T5UTY for combo obtained maintained as T in taxability column.
/Ixx wage type is generated when there is pre tax wage type that needs to be taken from employees taxable wages but cannot be taken resulting into generating /Ixx wage type which means pre tax amounts not taken.
Thanks<
Ameet