Dear Manjiri ji,
First of all, you need to clarify whether the supply and erection job of equipment/plant and machinery, which you are going to execute, is in an existing factory or in a factory under construction falling under the BOCW Act.
If it is in an existing factory, the BOCW Act is not applicable to any of the activities on the factory premises. If it is in a factory under construction, the BOCW Act is applicable to the entire worksite, including your supply and erection work. The Principal Employer and all the contractors under him employing 10 or more persons need to apply for and obtain an RC under the BOCW Act. Each beneficiary (in service for more than 90 days) is required to be registered with the Board under the BOCW Act.
According to me, Cess is payable by the PE in case your PE is non-PSU/Govt. U/T. However, the PE can make a recovery of the cess amount from your billing if it is provided in the agreement signed by you.
If the PE is PSU/Govt. U/T, cess is payable by you.
Regarding the License under CLA, if you are employing 20 or more persons, you are liable for the License. However, the PE is liable to endorse your details in his RC under CLA irrespective of the number of persons you employ.
Hope you find it in order.
Thanks with regards,
Keshav Korgaonkar