No, shift allowance is normally based on the number of shifts attended, and it's better to keep this separate from CTC. In general, there will be a different pattern for different shifts; for example, employees attending the First and General shifts are not generally eligible for shift allowance. The employees who work the Second and Night shifts will receive shift allowance.
Shift duties are to be rotated, and on public holidays and weekly offs, employees shall be paid overtime at double the rate. Hence, in general, companies do not pay shift allowance for these shifts. Sometimes, employees may mutually exchange shift duties.
If you include the shift allowance in CTC, regardless of their shift duties, employees will be eligible for that specific allowance, and it will become part of their salary.
Considering the above points, including the shift allowance in the CTC is not advisable.
Regards,
Kamesh