SDI (Sistema di Interscambio): How Italy's E-Invoicing Hub Works

Every Italian invoice that meets the legal definition of a valid B2B or B2G invoice has to pass through one specific place: the SDI — Sistema di Interscambio (the Electronic Exchange System).

You can think of the SDI as Italy's national invoice router. It sits between every sender and every recipient. There's no way around it: you send to SDI, and SDI delivers to your customer. No direct invoice delivery exists for Italian domestic B2B transactions.

This article explains exactly how the SDI works — what happens at each stage, what the different status notifications mean, and what you need to know to stay compliant.

What Is the SDI?

The SDI is a platform operated directly by the Agenzia delle Entrate (Italy's tax authority). It was designed with two purposes:

Ensure invoice validity — Every invoice is validated against the official FatturaPA XML schema before it reaches the recipient. Malformed, incomplete, or structurally incorrect invoices never reach your customer.
Create a full tax audit trail — Because every invoice passes through a government-controlled hub, the Agenzia has real-time visibility into all B2B transactions. This dramatically reduces VAT fraud and enables more targeted tax enforcement.

The SDI has been processing invoices since 2014 (initially for B2G) and handling mandatory B2B invoices since January 2019. By volume, it's one of the largest transaction processing systems in Europe.

The Invoice Journey Through SDI

Here's exactly what happens from the moment you click "send invoice" to the moment your customer's system receives it.

Stage 1: Transmission to SDI

You (or your intermediary software) submit the FatturaPA XML file to SDI. This can happen via:

Web service — Direct API integration, used by most e-invoicing software
FTP — For high-volume batch submissions
PEC (Posta Elettronica Certificata) — Certified email; slower, used as fallback
Agenzia delle Entrate web portal — For manual, low-volume submission

In practice, your e-invoicing software handles this automatically. You won't directly interact with SDI yourself.

Stage 2: SDI Validates the File

SDI checks the FatturaPA XML against the official XSD schema. This includes:

Schema validity (all required fields present, correct data types)
Logical consistency (totals match line items, VAT calculations correct)
Sender VAT number validity (checked against the Italian VAT register)
Recipient identification (CodiceDestinatario or PEC address present)

This validation happens within a few seconds to a few minutes for normal loads. During very high-volume periods (year-end, quarterly deadlines), it can take longer.

Stage 3a: Rejection — Notifica di Scarto (NS)

If validation fails, SDI sends back a Notifica di Scarto (NS — rejection notice). The invoice is not delivered to the recipient. It is as if the invoice was never sent.

The NS contains:

An error code
A description of what failed
The problematic XML element(s)

You have 5 calendar days from the date of the NS to correct the invoice and resubmit with the same invoice number and date. After 5 days, you must issue a new invoice with a different number.

Stage 3b: Delivery — SDI Routes to Recipient

If validation passes, SDI looks up the recipient using their CodiceDestinatario. It then delivers the invoice to the recipient's registered channel:

CodiceDestinatario → delivered directly to the recipient's intermediary system
PEC address → delivered to the recipient's certified email inbox
No channel registered → stored in the recipient's area on the Agenzia delle Entrate portal

Stage 4: Delivery Receipt — Ricevuta di Consegna (RC)

When the recipient's system successfully receives the invoice, SDI sends the sender a Ricevuta di Consegna (RC — delivery receipt). This confirms:

The invoice was delivered
The exact timestamp of delivery
The recipient's SDI code

This is the moment the invoice is legally "received." Payment terms typically run from this date.

Stage 4 (alternative): Non-Delivery Notice — Notifica di Mancata Consegna (MC)

If SDI can't immediately deliver the invoice (e.g., the recipient's system is temporarily unavailable), it sends a Notifica di Mancata Consegna (MC). SDI will then retry delivery for 10 calendar days.

After 10 days of failed delivery attempts, SDI issues a Notifica di Decorrenza Termini (DT) — see below.

Stage 5: Recipient Response (Optional)

After receiving the invoice, the recipient can formally accept or reject it via SDI:

Notifica di Esito Committente (EC):

EC01 — Accepted: The recipient confirms the invoice is correct
EC02 — Rejected: The recipient disputes the invoice (wrong amounts, wrong items, etc.)

This is optional — the recipient is not required to send a formal response. Most businesses don't use this in practice.

Stage 6: Automatic Acceptance — Notifica di Decorrenza Termini (DT)

If the recipient doesn't respond within 15 calendar days of delivery (or 10 days of MC notification), SDI automatically marks the invoice as accepted by deadline expiry. You'll receive a DT notification.

DT doesn't mean payment is due — it just means the invoice cleared the formal acceptance window. Your contractual payment terms still apply.

SDI Status Summary

Notification	Code	What It Means
Ricevuta di Consegna	RC	✅ Invoice delivered to recipient
Notifica di Mancata Consegna	MC	⏳ Delivery failed, SDI retrying
Notifica di Scarto	NS	❌ Invoice rejected — fix and resubmit within 5 days
Notifica di Esito Committente	EC01	✅ Recipient accepted
Notifica di Esito Committente	EC02	⚠️ Recipient rejected — follow up
Notifica di Decorrenza Termini	DT	✅ Auto-accepted (15-day window expired)

Your e-invoicing software should display these statuses in real time. If it doesn't, switch software.

SDI for Cross-Border Transactions

SDI is designed for domestic Italian transactions. For cross-border invoicing, different rules apply:

Sending invoices to foreign customers: Use TipoDocumento TD28. Submit to SDI like any other invoice. SDI won't validate the recipient (since they're foreign), but the transmission still creates the required tax authority notification.

Receiving invoices from foreign suppliers: You self-bill using the appropriate code (TD17, TD18, TD19) based on whether the supply is services, intra-EU goods, or non-EU goods. Submit the self-billing document to SDI to document the reverse charge.

This replaces the old esterometro quarterly reporting that was abolished from July 2022.

What the SDI Means for Your Tax Compliance

The SDI isn't just a plumbing system — it's how the Agenzia delle Entrate monitors your business in real time.

Every invoice you send or receive goes through a government system that can:

Cross-reference your declared revenue against transmitted invoices
Flag VAT discrepancies between sender and recipient records
Generate automated notices if your submitted invoices don't align with your VAT return (dichiarazione IVA)

Italy's e-invoicing system was explicitly designed as an anti-evasion tool. The Agenzia delle Entrate can now pre-populate much of the annual IVA return based on SDI data (this is the dichiarazione IVA precompilata project).

The practical implication: make sure your invoices are correct before transmitting. An incorrect invoice that gets delivered is harder to fix than one that gets rejected by SDI. Corrections require credit notes, not just a "sorry, here's the right file."

Practical Checklist Before Your First SDI Submission

Your partita IVA (VAT number) is active and correctly registered
Your software is configured with your RegimeFiscale code (RF01 for most, RF17/RF19 for forfettari)
You have a CodiceDestinatario registered with Agenzia delle Entrate (or you're using PEC)
Your conservazione sostitutiva service is set up and running
You have a test transmission confirmed with at least one invoice
You understand the NS notification and have a process for resubmissions

Last updated: April 2026. Sources: Agenzia delle Entrate — Specifiche tecniche SDI, Legislative Decree 127/2015.