It is a familiar story. A position becomes vacant in your organisation, you think long and hard about what is needed for an individual to be successful in that role and your mind automatically goes to a past employee. 

At AMS I have been fortunate to work with more boomerang employees than I can count. People have left for a variety of reasons, and having had valuable exposure and experience in the external market, have returned to AMS at a later date. The opportunity to bring back talent and leverage new expertise in a different context can have enormous upside for the individual and the organisation. 

Getting re-entry right can take a little bit of work. Dig deep to understand the reasons the individual wants to return. What has changed (and what has remained the same) for both parties which would lead to a new engagement to be successful. 

Don’t skip induction and onboarding. Make sure the returning employee has the opportunity to properly understand role expectations and company objectives, even if they have spent significant time in the business.

With the cost of settling in a new employee quickly adding up, tapping up past employees may prove to be one of the smartest hiring decisions you can make. 

Although it may seem like the employee is already well versed in the organization, a reintroduction is critically important. Treating the employee like they are new is a great way to reground them in your employment brand and get them excited about what has changed.

https://sloanreview.mit.edu/article/the-benefits-and-risks-of-rehiring-a-boomerang-employee/