What Is an EGS Unit? ZATCA E-Invoicing Terms Explained

What does EGS mean?

EGS stands for E-Invoicing Gateway Solution. In ZATCA’s language, an EGS unit is a single registered “unit” that can issue e-invoices—typically one device (e.g. a POS) or one software system (e.g. your ERP or an API) that produces invoices under one CSID (the cryptographic stamp ZATCA gives you).

Think of it as: one EGS unit = one logical “issuer” that has its own certificate (CSID) and its own chain of previous invoice hashes.

Why does ZATCA use EGS units?

ZATCA needs to know which system or device issued each invoice so they can:

• Tie each invoice to a specific certificate and taxpayer
• Enforce the previous invoice hash (PIH) chain: invoices from the same unit must be sequential and linked by hash
• Control how many “issuers” you have (e.g. one per branch or one per till)

So you don’t get one CSID for the whole company and reuse it everywhere; you register one EGS unit per device or system that actually issues invoices.

When do I need more than one EGS unit?

• Multiple branches or tills: If each branch or till issues its own invoices, ZATCA typically expects each to be a separate EGS unit (and thus have its own CSID and PIH chain).
• Multiple systems: If you have one ERP for B2B and a separate POS for B2C, you may have two EGS units—one per system.
• Single system, single location: One EGS unit may be enough.

Your solution provider or ZATCA’s guidelines can confirm the exact rule for your case. When in doubt, one EGS unit per distinct “issuing” device or application is a safe mental model.

How do I get an EGS unit?

1. Log in to the Fatoora portal
2. Start the process to onboard a new solution/device (register a new EGS unit)
3. Generate an OTP in the portal and enter it in your e-invoicing solution or API within the validity period
4. Your solution completes the technical steps (CSR, compliance checks if required) and receives the production CSID for that unit

After that, every invoice issued “from” that EGS unit must use that CSID and maintain the PIH chain for that unit only.

Summary

Term	Meaning
EGS	E-Invoicing Gateway Solution
EGS unit	One registered issuer (device/system) with its own CSID and PIH chain
CSID	Certificate/stamp from ZATCA for that EGS unit; used to sign invoices
PIH	Previous invoice hash; links invoices from the same unit in sequence

If you use an API like Esnad, you create one EGS unit in the dashboard per branch or system, connect each with an OTP from Fatoora, and then send invoice data to the API; it signs and clears/reports using the right unit and CSID.

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