PEPPOL with India’s e-Invoicing system

Let’s look at how PEPPOL fits into India’s e-Invoicing system, particularly focusing on the IRN (Invoice Reference Number) model — and how they can work together or be aligned for global or cross-border trade compliance.

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🇮🇳 India’s IRN System: A Quick Recap

India's e-Invoicing mandate is managed by the Goods and Services Tax Network (GSTN). Here’s how it works:

🔁 India e-Invoicing Workflow

1. Supplier creates invoice in their ERP in JSON format.

2. The invoice is sent to the Invoice Registration Portal (IRP).

3. The IRP:

   • Validates the invoice

   • Digitally signs it

   • Returns it with:

     • IRN (Invoice Reference Number)

     • QR Code

4. Only then is the invoice considered valid under Indian GST law.

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🔗 PEPPOL + India IRN: Integration Possibilities

❓ Why link PEPPOL and IRN?

If a company operates internationally or with government/public sector buyers, it might need to:

• Use PEPPOL for cross-border or B2G (business-to-government) procurement.

• Use IRN for compliance within India.

✅ Possible Workflow: PEPPOL + IRN Hybrid Flow

[Seller ERP]
   |
   |-- Generates eInvoice (PEPPOL BIS)
   |
   |-- Convert to IRN-compliant JSON (Gov format)
   |
   |-- Send to IRP (Invoice Registration Portal)
         |
         |-- Validation, IRN + QR Code issued
         |
         |-- Updated invoice (Signed JSON or embedded IRN+QR in PDF)
   |
   |-- Forward to Buyer via PEPPOL Access Point
         |
         |-- Buyer receives compliant eInvoice via PEPPOL

✅ Complies with Indian GST laws
✅ Meets PEPPOL document transport standards
✅ Enables global interoperability

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📌 Key Technical Integration Points

Aspect	India IRN Model	PEPPOL Model
Format	JSON schema (Govt-specified)	UBL XML (PEPPOL BIS standards)
Validation Authority	IRP (Invoice Registration Portal)	No central validator, peer-to-peer model
e-Signature	Mandatory (done by IRP)	Optional
Transport	API (pull/push to IRP)	AS4 over 4-corner model
Compliance Scope	Domestic B2B & B2G invoices	B2G and cross-border invoices

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🌐 Use Cases Where This Is Relevant

1. Multinational suppliers in India: Need IRN for Indian buyers, PEPPOL for foreign or government clients.

2. ERP/EDI providers: Want to build connectors that support both workflows.

3. Government procurement: If GoI adopts PEPPOL, vendors will need to do both IRN & PEPPOL transmission.

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🧠 Pro Tip

Some platforms (like ClearTax, SAP GRC, Avalara) are already working on bridges between IRP & PEPPOL formats. These tools can:

• Convert PEPPOL BIS invoice to IRP JSON

• Attach IRN and QR Code to UBL format

• Route the document via PEPPOL after validation

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Would you like:

• A diagram showing this flow? Below mentioned 

• 
  
  
  

• Info on tools/APIs that enable this?

Let me know how deep you’d like to go!

PEPPOL Functional Flow

 In the PEPPOL (Pan-European Public Procurement Online) framework, the procurement process is often divided into several stages that reflect the lifecycle of a procurement transaction. These are:

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1. Pre-Award Phase

This is the stage before a contract is awarded. It involves activities related to:

• Tendering (publishing and responding to procurement calls)

• Qualification and selection of suppliers

• Exchange of pre-contractual information

PEPPOL capabilities (documents) here may include:

• Pre-Award Catalogue (catalogues provided during tendering)

• Tenders and Tender Responses

• Call for Tenders

• Qualification Certificates

📌 Main Goal: Help organizations find suppliers and get offers (RFQs, RFPs).

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2. Post-Award Phase

This occurs after a contract has been awarded. It includes operational procurement and invoicing processes.

Common PEPPOL post-award documents:

• Order (PEPPOL BIS Order)

• Order Response

• Despatch Advice (Shipping notification)

• Invoice / Credit Note

• Catalogue (Updated post-award catalog)

📌 Main Goal: Exchange of e-procurement documents to fulfill the contract (ordering, delivery, billing).

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3. e-Delivery (Transport Infrastructure)

This is not a procurement phase but rather the technical infrastructure that supports the secure exchange of e-documents between trading partners.

PEPPOL uses a 4-corner model involving:

• Corner 1: Sender (e.g., Supplier)

• Corner 2: Sender’s Access Point

• Corner 3: Receiver’s Access Point

• Corner 4: Receiver (e.g., Buyer)

Standards used:

• AS4 (Secure Transport Protocol)

• SMP (Service Metadata Publisher)

• SML (Service Metadata Locator)

📌 Main Goal: Ensure secure, standardized document exchange without requiring point-to-point integrations.

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4. CTC Model (Continuous Transaction Controls)

This model relates to real-time or near real-time reporting of e-invoices to tax authorities, common in countries with mandatory e-invoicing regulations (like Italy, India, etc.).

• PEPPOL is increasingly adapting to support CTC models, where:

  • E-invoices must pass through a government or clearance authority before reaching the buyer.

  • PEPPOL Access Points integrate with tax authorities to comply with national laws.

📌 Main Goal: Ensure tax compliance, transparency, and reduce VAT fraud.

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Summary Table:

Phase	Purpose	PEPPOL Role
Pre-Award	Tendering, qualification	Pre-award catalogues, tenders
Post-Award	Ordering, delivery, invoicing	Orders, invoices, despatch advices
e-Delivery	Secure transmission of e-documents	AS4, SMP/SML, 4-corner model
CTC Model	Real-time tax reporting	Integration with tax authorities

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If you’d like, I can also show you how these fit into the overall PEPPOL architecture or workflows, or tailor this for a specific use case (e.g., government procurement or B2B).

Kind of AS2 Failures in EDI and How to Fix

 

✅ MDN Errors in AS2 – Overview and Resolution

In AS2 (Applicability Statement 2), an MDN (Message Disposition Notification) is an electronic receipt that acknowledges the successful or failed delivery of a message. When issues occur during AS2 communication, MDN errors are generated, indicating problems with message transmission, validation, or decryption.

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🔥 1. What is an MDN in AS2?

• An MDN is a receipt confirmation sent by the receiver to the sender, verifying whether the message was:
  • Received successfully
  • Decrypted correctly
  • Validated without issues
• The MDN contains:
  • Disposition: The final status (e.g., processed, failed, or rejected).
  • MIC (Message Integrity Check): A hash value used to verify message integrity.
  • Digital signature: To ensure authenticity.
• MDN types:
  • Synchronous MDN: Sent immediately after receiving the message.
  • Asynchronous MDN: Sent later (within a specific time window).

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🔥 2. Common MDN Error Types and Resolution

Below are the most common MDN errors encountered in AS2 communication, along with their causes and resolutions:

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🛑 ❗ 1. MIC Mismatch Error

Error:

MIC mismatch: Received MIC does not match the expected MIC

Cause:

• The Message Integrity Check (MIC) received in the MDN does not match the MIC calculated by the sender.
• This occurs due to:
  • Data corruption during transmission.
  • Incorrect hashing algorithm (e.g., SHA-1 vs. SHA-256 mismatch).
  • Data compression or encoding issues.

Resolution: ✅ Check hashing algorithm consistency:

• Ensure both sender and receiver use the same MIC hashing algorithm (SHA-1, SHA-256, or MD5).
• Go to Trading Partner → AS2 configuration → MIC Algorithm → Verify that both ends use the same hash algorithm.

✅ Check data integrity:

• Verify that the payload data and signature are not modified or corrupted.
• Re-transmit the AS2 message.

✅ Enable content transfer encoding:

• Ensure consistent encoding (e.g., Base64) to prevent corruption.
• In IBM Sterling B2B Integrator, enable Base64 encoding under AS2 settings:
  • Enable Content-Transfer-Encoding: Base64.

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🛑 ❗ 2. Signature Verification Failed

Error:

Signature verification failed. Invalid signature in the MDN.

Cause:

• The MDN signature does not match the sender’s signature.
• This occurs due to:
  • Expired or invalid certificate.
  • Incorrect partner certificate mapping.
  • Signature algorithm mismatch.

Resolution:
✅ Verify certificates:

• Go to Trading Partner → Certificate Management.
• Verify that the partner’s certificate is valid and not expired.
• Ensure the correct certificate is used for signing and verification.

✅ Certificate mapping consistency:

• Ensure the correct public certificate of the partner is configured in AS2 settings.
• Re-import the valid certificate if necessary.

✅ Update signature algorithms:

• Ensure both sender and receiver use compatible signature algorithms (SHA-1, SHA-256, or SHA-512).
• In Sterling B2B, go to:
  • Trading Partner → AS2 Configuration → Signature Algorithm
  • Verify the same algorithm is used by both sides.

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🛑 ❗ 3. Invalid MDN Format

Error:

Invalid MDN format: Missing fields or malformed MDN response.

Cause:

• The MDN received is incomplete or corrupted.
• Common causes:
  • Incorrect MIME formatting.
  • Empty MDN or missing content.
  • Incorrect AS2 header settings.

Resolution:
✅ Check MDN structure:

• Go to Operations → System Logs → AS2 logs.
• Inspect the MDN headers and body.
• Verify if the MDN contains:
  • Disposition: status
  • Content-Type: header
  • MIC: value

✅ Fix MIME formatting issues:

• Ensure that the partner uses standard MIME formatting.
• Add proper Content-Disposition and Content-Transfer-Encoding headers in the AS2 settings.

✅ Enable proper AS2 headers:

• Verify that the MDN includes:
  • Content-Type: multipart/signed
  • Content-Transfer-Encoding: base64

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🛑 ❗ 4. MDN Not Received / Timeout

Error:

MDN not received: Timeout error

Cause:

• The MDN was not received within the expected timeframe.
• This happens due to:
  • Asynchronous MDN delays.
  • Network issues.
  • Partner system issues.
  • Incorrect AS2 URL or port.

Resolution:
✅ Verify AS2 URL and port:

• Go to Trading Partner → AS2 Configuration → AS2 URL.
• Confirm that the URL and port are correct.
• Ensure that the AS2 URL is reachable:

telnet <partner_URL> <port>

✅ Check firewall settings:

• Ensure firewall rules allow AS2 communication on the required port (typically 8080 or 8443).

✅ Extend MDN timeout:

• In IBM Sterling, increase the MDN timeout to allow sufficient time for asynchronous MDNs:
  • Trading Partner → AS2 Settings → MDN timeout → 5-10 minutes

✅ Resend the message:

• If the MDN is not received, resend the AS2 message.

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🛑 ❗ 5. AS2 Decryption Failure

Error:

Decryption failed: Invalid private key or decryption error

Cause:

• AS2 message decryption failed due to:
  • Incorrect private key used for decryption.
  • Mismatched encryption algorithm.
  • Corrupted or invalid payload.

Resolution:
✅ Verify encryption certificate:

• Go to Trading Partner → AS2 Configuration → Certificate Management.
• Ensure the correct private key is configured for decryption.
• If the decryption key is incorrect, re-import the correct key.

✅ Ensure algorithm compatibility:

• Confirm that both sender and receiver use the same encryption algorithm (AES-256, AES-128, or Triple DES).

✅ Validate encryption settings:

• Check encryption preferences in Sterling:
  • AS2 Settings → Encryption Algorithm → AES-256

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🛑 ❗ 6. AS2 Compression Error

Error:

Invalid compressed data format

Cause:

• The message was compressed incorrectly or the receiver could not decompress it.
• This happens due to:
  • Unsupported compression algorithm.
  • Corrupted compressed data.

Resolution:
✅ Disable or update compression:

• If compression causes issues, disable compression temporarily.
• In IBM Sterling, go to:
  • Trading Partner → AS2 Configuration → Compression → Disable
• If compression is required:
  • Ensure both sender and receiver use compatible compression algorithms (ZLIB, GZIP).

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🎯 ✅ Key Takeaway: Resolving MDN Errors in AS2

To resolve MDN errors in IBM Sterling B2B Integrator:

1. Check MIC and Signature: Ensure MIC algorithms and certificates match.
2. Review AS2 configuration: Verify URL, port, and partner settings.
3. Increase MDN timeout: Allow more time for asynchronous MDNs.
4. Enable consistent encryption: Use matching algorithms on both ends.
5. Check logs and re-transmit: Inspect AS2 logs, identify issues, and resend the message.
6. Verify compression settings: Ensure compression compatibility.

✅ By systematically troubleshooting these MDN errors, you can effectively resolve AS2 communication issues.

PDF Container in XRechnung

 In XRechnung, a PDF container refers to a PDF document that contains an embedded machine-readable invoice in XML format, typically conforming to the XRechnung standard. This approach allows for a human-readable representation (PDF) and a machine-processable version (XML) of the invoice to be delivered together in a single file.

Breakdown:

• XRechnung is a German standard for electronic invoicing that is compliant with the European Norm EN 16931.

• The core requirement is to send an XML invoice that conforms to this standard.

• Some recipients, however, still prefer to view the invoice in a readable format — that's where the PDF container comes in.

The PDF container includes:

1. A visual representation of the invoice (PDF).

2. An embedded XRechnung XML file as an attachment inside the PDF/A-3 format (an ISO standard for archivable PDFs that allows file attachments).

Why use it?

• Helps bridge the gap between systems that can process XML and users who want to visually inspect the invoice.

• Common in B2G (Business to Government) settings where PDF readability is often still required.

Tools often used:

• PDF/A-3 compliant tools like iText, Apache PDFBox, or commercial invoice generation software.

• Embedded XML file is typically added as a file attachment with a specific MIME type and naming convention (zugferd-invoice.xml or similar).

Let me know if you’d like a sample structure or to generate one for testing.

PEPPOL End-to-End Workflow

Let’s walk through how Pre-Award, Post-Award, e-Delivery, and the CTC Model fit into the overall PEPPOL architecture and workflow — using a visual-style explanation of the PEPPOL end-to-end process.

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🔄 PEPPOL End-to-End Workflow (Conceptual View)

   [Buyer]                         [Seller]
     |                                |
     |--1. Pre-Award----------------->|   ← Tendering, RFQs, Pre-award catalogues
     |                                |
     |<-- Responds -------------------|   ← Bids, Quotes
     |                                |
     |== Contract Awarded ============|
     |                                |
     |--2. Post-Award---------------->|   ← eOrder (PEPPOL BIS Order)
     |                                |
     |<-- Order Response -------------|   ← Accept/Reject/Change order
     |                                |
     |<-- Despatch Advice ------------|   ← Shipping details
     |                                |
     |<-- Invoice --------------------|   ← eInvoice (PEPPOL BIS Invoice)
     |                                |
     |-- Invoice Response (optional)->|   ← Accept/Dispute
     |                                |

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🌐 PEPPOL e-Delivery (Behind the Scenes)

All the above documents flow via PEPPOL Access Points through a standardized 4-corner model:

[Seller System]
     ↓
[Access Point 1] -- AS4 Protocol --> [Access Point 2]
     ↓                                     ↓
[PEPPOL SMP/SML]                     [Buyer System]

• Access Points: Providers certified to send/receive PEPPOL documents.

• SMP: Directory service to find recipient capabilities.

• SML: Routes the messages based on recipient PEPPOL ID.

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🔒 CTC Model in PEPPOL (When Tax Authorities are Involved)

In countries with mandatory e-invoicing and real-time tax reporting, PEPPOL supports the CTC (Continuous Transaction Controls) model:

[Supplier ERP]
     ↓
[PEPPOL Access Point]
     ↓
[Tax Authority Portal / Clearance System]  ← Validation, archiving, e-signing
     ↓
[PEPPOL Access Point]
     ↓
[Buyer ERP]

• E-invoice is first validated/approved by the tax authority.

• Only after that, it is delivered to the buyer.

Countries exploring or implementing CTC + PEPPOL:

• Italy (FatturaPA)

• France (2026 planned)

• Poland, Greece, etc.

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🚀 Summary: Where Everything Fits

Stage	Key Docs	Infrastructure Used	CTC Role
Pre-Award	Tender, Quote, Pre-Award Catalogue	Access Points, SMP	Not applicable
Post-Award	Order, Invoice, Despatch, Credit Note	Access Points, SMP/SML, AS4	If invoice → routed via tax portal
e-Delivery	Applies to all document transport	4-corner model, AS4, SMP/SML	Enables compliant, secure exchange
CTC Model	Invoice or Credit Note only	PEPPOL + National Tax Systems	Mandatory validation/archival

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• Let me know what direction you want to explore!