I think that the query has been raised basically to ascertain whether the past service would get affected by the transfer. If the transfer is within the same organization, like an intra-departmental one, it will not affect the service rendered before the transfer.
Transfer of an Employee
The term "transfer of an employee" implies a change of post within the organization with or without a change of place. Therefore, the exchange of charges of the posts at both ends would certainly require the formalities of relieving and joining unless the transfer orders specify the holding of an additional charge of one of the posts simultaneously.
Certain posts involving the handling of materials or cash would require the assumption of charge of such assets on hand on the very date of joining. In such a situation, relieving or joining formalities cannot be skipped for the sake of administrative convenience.