EDI exception handling

• Every exception is picked up the moment it happens, from the translator, the business validation rules, a negative functional acknowledgement (CONTRL, 997 or 999) or a missing AS2 receipt (MDN).
• The agent reads the raw message, the error, the partner's implementation guide and the related order, ASN or receipt, then says what failed, why, and whose side the fix is on.
• Where the fix is ours, it proposes one: a master-data correction, a cross-reference to add, a mapping change to test, or a corrected outbound message staged for approval.
• Where the fix is the partner's, it drafts a note to their EDI desk from an approved template, quoting the interchange reference and the exact segment and value at fault.
• An analyst approves every resubmission. Replays run from the stored original, through the same validation, and an idempotency check means a replay can never create a duplicate order, ASN or invoice.
• Repeat causes are counted by partner and by root cause, so the integration team fixes problems at the source instead of clearing the same exception every day.

• Trading partnersTrading partner agreements and implementation guides
  →

  Each partner sets its own message versions, mandatory fields, timings and, often, charges for late or inaccurate ASNs. The agent works from the current version of each guide, held under change control, and every proposed fix is checked against that partner's rules before an analyst sees it.

• HMRCVAT invoices (VAT Notice 700) and correcting errors (VAT Notice 700/45)
  →

  An EDI invoice is a VAT invoice. If one is rejected, it is corrected at source and re-issued, or put right with a credit note, under finance's control. The agent never changes the amounts, VAT or tax point on an invoice in transit, and never edits a supplier's invoice to make it match.

• HMRCMandatory e-invoicing from 1 April 2029 (roadmap published 28 October 2026)
  →

  VAT invoices between VAT-registered businesses must be exchanged as structured e-invoices through Peppol, via a certified access point. PDFs and emails won't count. Existing EDI can continue, but the business must also be able to exchange e-invoices through the new framework, and HMRC plans guidance on EDI and legacy systems in autumn 2027.

• GS1 UKGS1 identifiers and EDI standards (GTIN, GLN, SSCC, EANCOM, GS1 XML)
  →

  Most business-rule failures are identifier problems: an unknown GTIN, a delivery location GLN that has changed, a reused SSCC. The agent checks identifiers against the product and partner master data and proposes corrections there, never in the message.

• ICOUK GDPR and the Data Protection Act 2018
  →

  Orders for home delivery and trade accounts carry names, addresses and phone numbers. That means a light DPIA, collecting only what's needed for diagnosis, masking personal data in prompts and logs where possible, a clear retention period, and a contract that stops providers training their models on your data.

• NCSCCyber Essentials and supplier assurance
  →

  The EDI gateway holds the keys that let partners trust your messages. AS2 private keys live in a vault or HSM, partner certificates are tracked with expiry alerts, access to the gateway is role-based, and the agent has no access to keys or connection settings at all.

On a phone, the table shows the platform you pick. Sovereign / on-prem means open, portable components you can run in your own data centre or with a UK or European provider; IONOS is shown as one example, and others exist. What sovereign cloud means →

• An exception taxonomy agreed up front (transport, envelope, syntax, code list, master data, business rule), so the agent, the analysts and the reports use the same words.
• Approval rules: which exception types an analyst approves alone, which need the integration team, and which go to finance.
• A library of approved partner templates, owned by the EDI lead, with the analyst editing and sending each one.
• A monthly repeat-cause review by partner, feeding fixes back into mappings, master data and partner onboarding.
• A certificate and connection register with named owners and expiry alerts, including partners' certificates as well as your own.
• A named owner for every prompt, partner guide and mapping spec in the index, with change control like any other integration artefact.

1. 2–3 weeks

   Discovery

   Export three months of exceptions, classify them by layer and root cause, measure time to resolve, and check access to the archive, translator logs and partner guides.

2. Gate · must be true to passBaseline agreed, top exception types and partners chosen, archive and log access confirmed, DPIA started.

3. 6–8 weeks

   Pilot

   Inbound orders and outbound ASNs for the five busiest retail customers, in shadow mode: the agent diagnoses and proposes, analysts work as normal, and the two are compared. Idempotency checks go live first, before any automated replay.

4. Gate · must be true to passDiagnosis agreement within agreed limits, zero duplicate postings in replay testing, and EDI lead sign-off.

5. 4–6 weeks

   Production

   Proposals and staged replays go live for the pilot partners, with monitoring, the approval rules and a rollback plan.

6. Gate · must be true to passMonitoring, support model, approval rules and analyst training in place.

7. Ongoing

   Scale

   Add invoices (with finance), supplier flows and the 3PL one at a time, then use the same pipeline when Peppol e-invoicing arrives.

8. Gate · must be true to passEach new flow passes the same pilot gate.

R ResponsibleA AccountableC ConsultedI Informed· not involved

Where I'd fit

1. 1

   Goes wrong

   The agent "fixes" a message by editing its contents, and the ERP now holds an order the customer never sent.

   How the design avoids it

   Partner content is never edited. Fixes go into master data, cross-references or mappings, and the stored original is replayed.

2. 2

   Goes wrong

   A resubmission posts the same order or invoice twice.

   How the design avoids it

   Idempotency keys checked before every posting, so a replay of something already posted does nothing.

3. 3

   Goes wrong

   An AS2 certificate expires on a Friday night and a major customer's orders stop.

   How the design avoids it

   A certificate register with alerts well ahead of expiry, a renewal runbook agreed with each partner, and monitoring for missing MDNs.

4. 4

   Goes wrong

   The same exception is cleared by hand every day for months.

   How the design avoids it

   Repeat causes counted by partner and root cause, with a monthly review that fixes them at the source.

5. 5

   Goes wrong

   A partner receives an off-script email that promises something the business can't do.

   How the design avoids it

   Approved templates only, and an analyst edits and sends every note.

1. 15 March 2027, then 15 March 2029
   Public TLS certificates already last at most 200 days (since 15 March 2026). The maximum falls to 100 days in March 2027 and 47 days in March 2029, under a CA/Browser Forum decision.

   If partners reach your AS2 endpoint over HTTPS with a public certificate, automate its renewal now, and keep the AS2 signing and encryption certificates in the same register.

2. Spring 2027 to 1 April 2029
   Mandatory B2B and B2G e-invoicing on Peppol. HMRC plans a technical consultation on standards and access point certification in spring 2027, guidance on EDI and legacy systems in autumn 2027, and go-live on 1 April 2029.

   Keep one canonical invoice model, so the same invoice can go out as EDIFACT, X12 or Peppol. Choose a certified Peppol access point provider rather than building one.

3. Expected 2027
   The Commercial Payments Bill, introduced in May 2026 and still before Parliament, would cap payment terms for large firms paying smaller suppliers at 60 days and make late-payment interest mandatory.

   Measure the days lost to rejected invoices now. Faster fixes for invoice exceptions will matter more once terms are capped.

4. Late 2026 to 2028
   The Cyber Security and Resilience Bill brings medium and large managed service providers into regulation, with duties set by secondary legislation by about 2028.

   If a managed provider runs your EDI or VAN, expect new duties on them and update your contracts and supplier assurance.