What industry are you in?
12-hour shifts in specific industries
12-hour shifts are only allowed in certain industries, such as hospitals or any workplace where there is an emergency. Other than hospitals, to the best of my knowledge, there is no place where 12-hour shifts are allowed.
Exceptions for maintenance roles
As an exception, certain individuals, mainly in maintenance roles, may be permitted to work 12-hour shifts as it is not feasible to interrupt maintenance work midway. However, they must be listed in Section 68 of the Factories Act (and the relevant rules) and documented in the appropriate registers. Even then, this remains an exception and cannot be transformed into a continuous 12-hour shift pattern.
Overtime compensation
Notably, when working 12 hours in a day, 4 hours will be compensated at double the regular overtime rate (double the gross pay, not double the basic pay).