While others have responded to your query, let me add my thoughts as well.
Retirement Policy and Re-employment Options
The policy of your company is that employees must retire at the age of 58 years. However, it is the desire of the company to re-employ the person after formal retirement takes place. There is no statutory requirement for retirement, as far as private companies are concerned. You are free to decide either way (re-employ the person or retain the person as a consultant) and also change the age of retirement as is felt appropriate.
Suggestions for Post-Retirement Engagement
1. Let the retirement take place, followed by the full and final settlement in the normal course.
2. It is preferable (as suggested by several others already) to retain (not re-employ) the person as a consultant. This would provide continuity and benefit from the knowledge that the individual brings to the table. I would not suggest that he be re-employed as an employee, since (apart from having to change the policy) this could be cited as a precedent by others who may retire later and seek re-employment. On the other hand, a company is free to appoint anyone as a consultant - it will not be possible to cite this as a precedent.
3. Regarding the allowances that would have been payable to the employee during his employment period (PF, EDLI, Gratuity, etc.), you could take a Cost-to-Company approach, i.e., gross up all the allowances payable as a part of salary and pay the person the grossed-up amount as consultancy fees. This would ensure that while the individual is no worse off financially, they also retain the flexibility to invest the surplus funds in instruments of their choice. Since a consultant is not an employee, benefits like PF/Gratuity, etc., would not be payable.
I hope this helps you in arriving at an appropriate decision.
Regards,
Raju Bhatnagar