3770277 - WBS Purchasing block bypass via service entry sheet when Purchase order uses account assignment U

WBS elements flagged as blocked for purchasing can still receive postings through Service Entry Sheets when the Purchase Order was created with account assignment category "U" and the SES is subsequently posted with category "P".

 SAP S/4HANA Cloud Public Edition

1. Create a WBS element and set it to blocked for purchasing.
2. Create a Purchase Order using account assignment category "U".
3. Create and post a Service Entry Sheet for that PO item using account assignment category "P" and select the same blocked WBS element.

Standard design evaluates the WBS “blocked for purchasing” check during PO account assignment validation at save time. With account assignment category "U", no WBS exists on the PO, so no check occurs. The SES process does not re-run the PO account assignment validations, which allows the bypass.

The standard system design allows this bypass behavior, making custom enhancement necessary to achieve complete purchasing block enforcement across all MM document flows. Implement a custom validation on Service Entry Sheets to enforce the WBS purchasing block. Use  BAdI MM_PUR_S4_SES_CHECK_HEADER to validate SES account assignments.

BAdi MM_PUR_S4_SES_CHECK_HEADER triggers an error message for Blocked WBS element in Service Entry Sheet creation . 

• Refer to: 3459521 - Creation of purchase document possible against blocked WBS Element
• Refer to: Project Element Blocked Function | Help Portal

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