Which function module sets the zero stock check indicator?

Hi SAP gurus,

I want to know, which function module is setting the zero stock check indicator during the creation of the transfer order (TC LT04). When a zero stock check has to be executed, the field LTAP-KZNKO is set to X (zero stock check yes) and the field LTAP-NULKO is set to 1 (zero stock check to be carried out (system)).

I'm not an ABAP developer, but I've tried to debug LT04 and similar programs with no result.

Please help. I'm looking forward to hearing from you 😊

Best regards,

Gunnar