Accounting coding block missing Sales Order COBL-KDAUF

Hello Experts,

I wish to have the Sales Order Number on the Financial document in the coding block. This does not seem to be passed from the Billing document as the field COBL-KDAUF is empty.

I have seen a number of other posts and questions where people are looking to do the same, but have it only populating for some documents or none. However, all of these questions are unanswered.

If someone is able to help, please advice if this is possible and the settings required.

Thanks,

R