A Shopify PO number is the buyer’s purchase-order reference on the draft or the order, so their accounts payable can match your invoice to their document. Add it when you create the draft. If a PDF or email workflow builds that draft, look at the number before you convert.
Why the number matters
The buyer’s AP team matches your invoice to their PO. Your Shopify order name (#1042) means nothing in their system. The PO number is also what you search when they dispute a line, and what sales quotes when they reorder. Missing it does not block Shopify. It blocks getting paid on their timeline.
Where it lives
On a draft or order, Shopify has a purchase order number field (wording in admin has been “PO number”). It is separate from notes and from the order name. Shopify moves labels. If you do not see it, look on the draft’s additional details rather than pasting the number only into a staff note. Notes get missed on the invoice. The PO field is what B2B documents expect.
POinbox uses Shopify’s own PO field. Use that unless your theme or checkout already standardized on something else your finance team reads.
Add it when you create the draft
Create the draft, add the customer, and type the buyer’s number before you save. The click-path is in how to create a draft order. Copy it from the PDF header, not from the email subject, when the two disagree. The header is the document. The subject is someone being helpful.
When the PO arrives as a PDF or email
POinbox turns the file into a reviewable draft. When the purchase order has a number, that number is written onto Shopify’s PO field, into a po_number attribute, into the draft note, and onto a po: tag. A second file with the same number is flagged as a duplicate, or as a possible revision, so the new copy sits next to the one you already have. During review, read the PDF header next to that field so the revision is the number that ships.
That review is the same moment you check lines and prices. Product page: POinbox. The B2B context is draft orders for purchase orders.
After you convert
The number should still be on the order. Check one converted draft before you trust the habit. Convert a draft order to an order covers the rest of that handoff. If it drops off, put it back before you send the invoice. Their AP queue will not infer it.
Where the number gets lost
It gets lost in a staff note. The invoice does not print the note, and the buyer’s AP clerk searches their PO number against your invoice and finds nothing. It gets lost when someone copies the email subject, which says “PO 4401 revised,” while the PDF header says 4401-B. Use the document, not the subject. It gets lost when a second revision arrives and the draft still wears the first number. Update the field before you convert. Their system will reject the invoice that cites the dead revision.
Shopify’s order name is yours. Leave it. The PO field is theirs. If your admin build hides the field under additional details, show new staff that screen once. Do not invent a metafield unless finance already reads that metafield on the invoice. A second place to type the number is how the two copies diverge.
When POinbox builds the draft from a file, the number from that file is already on Shopify’s PO field. Open the header and the field side by side so the document number, not the email subject, is the one on the draft. Convert once it matches.