There is no law till date for governing the retainership
The basic defference with the retainers of an employee is that employees are answerable for their work to a superior, where retainers are just like experts or consultants who are being paid for their expertise work only.
should you have any query in future do revert.
Fixed Term/ Contaract employee engaged by the Company will have applicability of Company's Standing Orders either certify or Model.
So far Retainer are concern they are not employee. The Company should fixed terms and conditions. But in practical situtation they should not be considered employee either in writing or in practice,
This is a seperate engagement where the person/ consultant is engaged for specific job
not as a regular employee. Do not fixed working hours or weekly off or leave as like Company's employee. If you do so he may get disadvantage .