As I understand, there is no definition of employer and employee in provisions of GST. In Income-tax Act also there are different heads of income for computation purposes to determine taxable income after allowing some relief and deductions and also denying some deductions though expenses may be incurred.
Therefore, general aspects related to employer and employee are to be considered. Tax deduction under particular provision or inclusion of income under any particular head under Income tax Act are not conclusive for GST/ services.
For employment, in context of service tax, essential aspects are responsibility and accountability to do some work and report progress. The work can be specified or can be unspecified. Accordingly there will be combination of work done and time reserved for doing such work. Reward will be for work and time both. In some situation even if no work is done or less work is done yet reward is basically dependent on time, and in some situations reward is fixed for work likely to be done and time reserved.
Work is done and reported from time to time to employer/ principal. Ultimate decision of employer will prevail and ultimate responsibility will be of the employer.
There must be relationship of principal and agent in such a manner and situation that the agent is responsible for doing some work and has to report to principal. He is not responsible to any other party in relation to work done by him. Ultimate responsibility in relation to such work is that of principal / employer and not of agent / employed person. In that case there is employer –employee relationship exists in the context of service tax or GST
However, when agent ( employed person) is having ultimate responsibility in relation to work done by him not only to employer but also to third parties, then employed person will be independent of employer and will be a service provider as independent person providing services.
Remuneration can be called by any name or nomenclature, it can be determined and discharged in any manner that will not be conclusive.
The accounting treatment , and disclosures in documents , incidental aspects which are specific to laws governing employment like PF, ESI, Gratuity, pension,profession tax etc. will be considered prima facie and main evidences of employment.
This is likely to be highly contentious issue if dispute arise.