Normally we create a Batch Order directly from Sales order, so the Sales Order line and Production order can be linked.

However, currently we can only create Batch Order under the same site as populated on Sale order line.

It could happen that we have a Sales order with Site A but need to arrange the production under another site (say Site B). Once production is finished, the finished goods will be transfer from Site B to Site A and sold from Site A.
So the reference number on the Sales order line will still showing the Batch Order.