C2B00012C2B / B2C resultM-Pesa error C2B00012: Invalid Account Number (Reject)
This is a C2B / B2C result code — it applies to customer-to-business validation or business-to-customer disbursement flows.
What causes it
During C2B validation the account number / bill reference supplied by the payer does not exist in your system.
How to fix it
Return this reject code for unknown account references, or map/create the account before accepting.
How paylod handles this
paylod records and decodes every C2B and B2C result, and lets you test the flow without hosting your own validation and confirmation callbacks — so you spend less time on Daraja plumbing and edge-case result codes.
See the paylod M-Pesa API