A 'job worker' under GST is defined as someone who performs a treatment or process on goods belonging to another registered person. Crucially, ownership of the goods remains with the principal, not the job worker. This definition is key for understanding GST implications on such services, which can include activities like construction work.
Section 2(68) of the CGST Act, 2017 defines job work as 'any treatment or process undertaken by a person on goods belonging to another registered person'. The one who does the said job would be termed as 'job worker'. The ownership of the goods does not transfer to the job worker but it rests with the principal.