Error in posting - Internal Orders

Dear Forum,

The users are trying to post the FI Document with the orders entered in the order field. However, the system does not allow the postings and gives the error message - FI Posting not allowed (Order xxxx).

Could you please advise what needs to be checked in the system to resolve the error. The users are new in using the concept of Internal Orders.

Thanks for the help!

Regards

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