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X12 segment reference
BAK — Beginning Segment for PO Acknowledgment
X12 BAK segment on EDI 855 PO acknowledgements: acknowledgement type, PO number, and status codes suppliers send back to retailers.
BAK segment facts
- BAK03 must echo the retailer's PO number exactly — formatting differences (leading zeros) cause 855 rejects.
- BAK02 RJ triggers buyer workflows — include PO1 line detail with reason codes when rejecting or changing quantities.
- Retail scorecards track 855 latency separately from ASN — treat BAK timing as a first-class SLA.
What the BAK segment does
BAK opens an 855 purchase order acknowledgement. BAK02 type codes (AC=acknowledge with detail, AD=accept, RJ=reject) tell the retailer how you intend to fulfill the PO.
Common transaction sets: 855
Key elements
| Element | Name | Description |
|---|---|---|
| BAK01 | Transaction set purpose code | 00=original, 05=replace. |
| BAK02 | Acknowledgement type code | AC, AD, RJ — retailer programs define allowed values. |
| BAK03 | Purchase order number | Must match BEG03 on the inbound 850. |
| BAK04 | Date | Acknowledgement date in CCYYMMDD. |
Example BAK segment
BAK*00*AC*PO-1042*20250609~
Parse and validate samples with the free EDI validator or send JSON via the JSON→X12 mapping guide.
Common BAK errors
- BAK03 PO number mismatch
- RJ without line-level reason codes
- Late 855 after ship window
Related reference
FAQ
Frequently asked questions
Many retailers mandate 855 within SLA after 850 receipt — check partner requirement pages before go-live.
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