Please can someone confirm if we can achieve inter company workflow approvals.
For example PO raised in one entity and required to be approved in another entity or raised and approved PO in one entity and simultaneously required to be approved in other entity too.
If yes, then kindly guide me on steps.
As Aamir implies this is not possible. You have a relationship already established within the legal entity, if you have configured this then "approval" is not really a requirement for the chain. It is supposed to ease the process. You could have the creation process decoupled and have certain people able to process the connected orders, but really it depends why this is being asked which is not explained.