Key Takeaways
- “Accepted by the mail server” proves an invoice reached the customer’s domain, not the AP queue.
- Collection is getting slower: global DSO rose from 47.3 days in 2015 to 50.0 days in 2024 (PwC, 2025).
- Resend once, under the original invoice number marked as a copy, so the customer cannot pay it twice.
- CollectPulse actions 100% of overdue invoices within 24 hours, against 30-40% for manual teams (Transformance customer data, 2026).
In This Article
- Key Takeaways
- What should you check first when a customer says the invoice never arrived?
- Where do invoices go missing between you and the customer’s AP?
- What do e-invoice status codes tell you?
- How do you tell a genuine miss from a delay pattern?
- What should you send the customer, and how?
- Should reminders pause while you resend?
- How do you stop “invoice not received” from happening again?
- How does Vero handle a customer who says the invoice never arrived?
What should you check first when a customer says the invoice never arrived?
Check the send record first: recipient address, timestamp, invoice number and whether the receiving server accepted or bounced the message, then ask which channel the customer’s AP team processes.
Delivery questions cost days, and collection is already slowing: global days sales outstanding (DSO) rose from 47.3 days in 2015 to 50.0 days in 2024, and by 5.5% in North America over the decade, across more than 17,000 listed companies (PwC, Working Capital Study 25/26, 2025).
The send record lives in your ERP output log, billing tool or e-invoice provider. “Accepted by the customer’s mail server” only proves the message reached their domain; it can still sit in a former buyer’s inbox, a quarantine folder or a parked approval workflow, unseen by accounts payable (AP).
The order of checks before you resend:
- Find the send record: recipient, timestamp, message ID, attachment.
- Read the outcome: accepted by the server, bounced, or rejected by an e-invoice or portal step.
- Compare the recipient with the AP contact in the customer master and the date that contact last changed.
- Check the invoice face for the PO number and the customer’s correct legal entity.
- Check the e-invoice or portal status, if the customer uses one.
- Check the customer’s history: earlier “not received” claims and how they ended.
- Only then resend once, on the confirmed channel, and ask one question: the AP address or the PO.
Where do invoices go missing between you and the customer’s AP?
Six handovers can lose an invoice: the send itself, the spam filter, the recipient, the purchase order check, the receiving legal entity and, for e-invoices, the format validation.
Two causes are common in enterprise accounts. Invoices sent to the person who placed the order sit in an inbox AP never sees, so record one AP address per customer entity. And many AP teams cannot route an invoice without a purchase order number, so it is parked and the customer truthfully reports “we don’t have it”.
What do e-invoice status codes tell you?
If you invoice through Peppol, the buyer’s Invoice Response turns receipt into a status code: acknowledged, in process, under query, conditionally accepted, rejected, accepted or paid.
Read the code before you resend (OpenPeppol, 2024). AB means the buyer received a readable invoice, UQ means AP needs more information before it accepts, and RE means AP will not process the invoice further. Three clarification reasons map straight onto “never arrived” (OpenPeppol, 2024):
- REF, references incorrect: references needed for routing are missing, typically the PO.
- REC, receiver unknown: the addressed party is not known.
- UNR, not recognised: the buyer does not recognise the transaction.
Many buyers send no Invoice Response, so a missing status is not proof of receipt. Background: e-invoicing and cash application.
How do you tell a genuine miss from a delay pattern?
A genuine miss leaves a trace, such as a bounce, a rejection reason or a changed contact; a delay pattern repeats across invoices while the delivery records stay clean.
Signals of a pattern: a third claim within a few months, claims that arrive only after a reminder, invoices already acknowledged (AB) or opened in a portal, and claims on large invoices only.
Respond the same way either way: evidence, not accusation. Send the record and the copy, keep your cadence, and route repeat cases to the account owner through your escalation matrix.
Illustrative example (figures are fictional): one customer reports three invoices “not received” in five months: EUR 18,400, EUR 22,750 and EUR 31,900, each with a clean acceptance on the AP shared mailbox. Taken together they form a pattern, so the third reply goes to the account owner with all three records attached.
If the customer then names a reason (price, quantity, damage), it has become a dispute: see AI dispute management in accounts receivable.
What should you send the customer, and how?
Send one short message on the confirmed channel: the original invoice number and PDF, the PO reference, the delivery evidence, and one question about what AP needs to release it.
Subject: Invoice [number], EUR [amount], due [date]: copy attached
Hello [name],
Attached is a copy of invoice [number] for EUR [amount], PO [PO number], due on [date]. Our records show it was sent to [address] on [date] and accepted by your mail server.
Could you confirm that [AP address] is the right address for our invoices, or tell us which portal or e-invoice route AP needs?
Kind regards,[name]
- Never issue a new invoice number. Mark the resend as a copy. If the PO must appear on the invoice face, follow your billing policy (credit and re-invoice) rather than editing the original.
- Send to the AP shared mailbox, copy the buyer, and log the answer against the customer so the next invoice goes to the right place.
The cadence after the hold: dunning process email templates.
Should reminders pause while you resend?
Hold the next reminder for the working days your collections policy sets after the resend, then resume unless a rejection, query or dispute comes back. If nothing comes back at all, see what to do when a B2B customer goes silent on overdue invoices.
Tag the case as a delivery query, separate from a dispute, so reporting shows how much overdue cash delivery problems block. Do not reset the dunning level or change the due date unless your policy says so.
Once AP confirms receipt, ask for a payment date and track it as a promise, as in how AI tracks promise to pay.
How do you stop “invoice not received” from happening again?
Prevention sits in master data and sending setup: one verified AP address per entity, PO numbers captured at order entry, the customer’s required channel recorded, and an authenticated sending domain.
Since 1 February 2024, Gmail has required SPF or DKIM from every sender to Gmail accounts, and SPF, DKIM and DMARC from senders of more than 5,000 messages a day (Google, 2024). Unauthenticated invoice mail risks the spam folder. Reminders face the same filters: see why dunning emails land in spam.
- Put the invoice number in the subject, one invoice per email.
- Confirm receipt of each new AP contact’s first invoice.
- Re-verify the contact when an email bounces or a new name replies.
How does Vero handle a customer who says the invoice never arrived?
Vero, Transformance’s AR agent, reads the customer’s Customer 360 history, checks contacts and earlier claims, drafts the resend message with its evidence, and a person approves before anything goes out.
Transformance sends payment reminders, not the invoices themselves, so checking the send log stays a person’s step. Vero adds memory: Customer 360, one graph per customer holding the contacts and when they changed, orders and invoices with their PO references, disputes and past resolutions, including earlier “not received” claims.
Vero reads the reply against that history and shows the collector where it points: an AP contact that changed last month, a PO reference missing from the invoice, or a third claim this year. It drafts the resend with that evidence; the collector adds the invoice copy and send record, and approves. In the 4-level approval model (read, recommend, execute, post), the draft is a recommendation, and sending is an execute step a person approves.
CollectPulse actions 100% of overdue invoices within 24 hours, against 30-40% for manual teams (Transformance customer data, 2026), so a “never arrived” reply comes in days after the due date, not weeks.
If AP goes quiet after the resend, the AI calling agent can call to capture a payment date or the reason, in 70+ languages; it identifies itself as AI at the start of every call. More in how AI automates collections and on the collections solution page.
Conclusion: find the trace before you resend
“Never arrived” is usually an acceptance problem inside the customer’s AP, not a lost email. Read the send record, the contact, the PO and the customer’s history first, then resend once with the evidence.
Frequently Asked Questions
What do you do when a customer says they never received an invoice?
Check the send record, the AP address and the PO first, then resend once on the channel AP processes, under the same invoice number.
Should you give the invoice a new number when you resend it?
No, resend the original invoice under its original number, marked as a copy, so the customer’s AP cannot book or pay it twice.
How do you prove an invoice was delivered?
Keep the send log (recipient, timestamp, message ID, server response) plus any e-invoice or portal status: it shows what left your system and what came back.
What if the same customer keeps saying the invoice never arrived?
Treat it as a pattern to resolve with records, not a judgement on the customer: send the delivery evidence and the copy, keep your cadence, and route the account to its owner.
Can an AI agent handle “invoice not received” replies?
Yes, an AI agent such as Vero from Transformance reads the reply and the customer’s Customer 360 history, drafts the resend with its evidence, and a person approves before it is sent.
