In case of decentralised treasury function does all the companies in a group have separate treasury department? Or a separate treasury department is only there in a centralised treasury function?
When decentralised then each company will have its own treasury function, whereas if centralised there is just one treasure function for the whole group.
Centralised is generally regarded as being a better approach because (for example) they can pool together foreign currency dealings in the separate group companies and benefit from better exchange rates; also they can pool together the depositing of spare cash in individual companies and so potentially get better interest rates.