Good question. We have been grappling with this as well.
Factories Act and Leave Policies
The Factories Act requires all workers to be given annual leave, including contract labor. There is no mention of leave encashment in the Factories Act. Instead, it provides for a maximum carry forward of the number of leave days.
As a general practice, leave encashment is a bad idea; workers should be given leave. If you are providing leave encashment, definitely ensure that it's done annually and not on a monthly basis, which is a practice that lots of contractors follow to avoid the trouble of keeping leave records. Giving monthly leave encashment leaves a trail and documentary evidence that workers were denied leave (by paying monthly, you are ensuring that they do not have accumulated leave).
If you are paying leave encashment on a monthly basis, and if you are marking all persons as leave without pay for absence during the year, the same problem will arise - that you are denying them leave. This can be considered a bad labor practice as well as exploitation of contract workers, which can lead to further problems.
If anyone has a different point of view, please enlighten me.