In SAP, a Debit Note is usually processed through billing or financial accounting, depending on the context (SD or FI module).
Here are the main tcodes:
SD (Sales and Distribution) Module:
VF01 – Create Billing Document (use with Debit Note billing type, e.g., L1 or DR)
VA01 – Create Sales Order (with order type DR for Debit Request, which can lead to a debit note)
FI (Financial Accounting) Module:
FB01 – Post Document (general, can be used to manually post a debit note)
FB70 – Outgoing Invoice (can simulate a debit note to a customer)
