Why PO numbers turn into invoice friction
A purchase order number often sits between your WooCommerce order and the buyer’s accounts-payable approval. If the number is missing from the PDF, entered after the invoice is issued, or excluded from exports, support gets stuck resending documents and finance gets stuck reconciling exceptions.
The safer workflow treats the PO number as invoice metadata: captured early, printed on PDFs, logged when changed, linked to proforma and credit-note events, and included in accounting exports.
PO invoice readiness checklist
1. Capture the PO number before the invoice is issued
B2B buyers often require a purchase order number before accounts payable will approve payment. The PO field should be captured at checkout, order review, or manual proforma creation before the final invoice PDF is generated.
Buyer question: Can the plugin store a PO number as invoice metadata before the PDF number is locked?
2. Print PO references on every relevant PDF
A PO reference should appear on proformas, final VAT invoices, credit notes, customer downloads, and email attachments. If it only appears in an admin note, the customer’s finance team may reject the document.
Buyer question: Will the PO number appear on the customer-facing PDF and not just inside WooCommerce admin?
3. Keep PO approval evidence with the order timeline
Finance teams need to see who supplied or changed the PO number, when the proforma was sent, when the final invoice was issued, and whether any correction or credit note changed the customer balance.
Buyer question: Can support and accounting review PO changes, email sends, downloads, and related credit notes in one timeline?
4. Separate proforma requests from final VAT invoices
For bank-transfer or enterprise orders, a proforma may include the PO reference before payment. The final VAT invoice should be issued after payment or fulfilment according to your workflow, with the same reference retained.
Buyer question: Does the plugin support proforma-to-final invoice flow without duplicating invoice numbers?
5. Export PO fields for accountant handoff
Accountants and finance ops need invoice number, order number, PO number, VAT totals, reverse-charge status, payment status, due date, and credit-note links in exports — not a manual copy from private notes.
Buyer question: Can invoice exports include the PO reference and payment context your accountant actually needs?
Three PO invoice scenarios to test
Enterprise buyer requires PO before payment
Trigger: The customer cannot pay a BACS/proforma invoice unless the PDF contains their internal PO number.
Workflow: Capture the PO, issue a proforma with payment terms, retain send/download evidence, then generate the final VAT invoice with the same PO after payment.
PO number arrives after checkout
Trigger: The buyer placed an order but finance sends the PO reference later by email.
Workflow: Add the PO as controlled invoice metadata, log who changed it, resend the invoice PDF, and keep the previous send evidence visible.
Refund or correction after PO approval
Trigger: A customer needs a credit note or corrected invoice for an order that already has a PO-approved final invoice.
Workflow: Retain the original invoice, issue a credit note or replacement workflow with the PO reference, and export both documents for accounting reconciliation.
Manual workaround vs invoice-ready workflow
| Manual workaround | Lattice Invoices direction |
|---|---|
| PO number stored in a private order note | PO field tied to invoice PDF, proforma, email resend, customer download, and export metadata. |
| Finance edits an issued invoice PDF manually | Controlled correction path keeps original invoice retained and logs PO/correction changes. |
| Accountant receives a CSV without PO references | Export includes invoice number, PO number, VAT totals, due date, payment status, and credit-note links. |
Early-access offer: €49 PO invoice workflow review
Send your current invoice plugin, checkout fields, proforma/BACS process, PO-number pain points, and accountant export needs. Lattice will map where PO evidence should be captured, printed, logged, and exported before you automate it.
Send my PO invoice workflowFAQ
Can WooCommerce add purchase order numbers to invoices by default?
WooCommerce can store order metadata, but invoice-safe PO workflows usually need a visible field, PDF template placement, proforma support, resend logs, customer downloads, and export fields.
Should PO numbers be editable after an invoice is issued?
If a PO reference must be corrected after issue, the change should be logged and visible. Stores should avoid silently rewriting historical invoice evidence without an audit trail or correction workflow.
Do PO numbers matter for EU VAT invoices?
A PO number is not the same as VAT evidence, but B2B customers often need it for approval. The invoice still needs invoice number, seller/buyer details, VAT or reverse-charge wording, totals, and retained PDF evidence.
Where does Lattice Invoices fit?
Lattice Invoices is the early-access WooCommerce EU invoicing path for stores that need PO references, proforma PDFs, final VAT invoices, credit notes, customer downloads, reminder evidence, and accountant-ready exports.