Audit missing receipts is not working

Summary:

We have a requirement to audit all expense reports that has an expense where employee selected "Missing Receipt" check box. We have setup receipt requirements at template level

And also selected the check box to Audit expense reports with missing imaged receipts in Audit selection rule and assigned it to the BU

However, when employee submits the expense report and select Receipt Missing, the expense reports are ready for payment after approval. They are not selected for audit. Can you please confirm if anything else need to be setup or this is a bug in oracle?

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