ICCID

The ICCID (Integrated Circuit Card Identifier) is the serial number of a SIM. On a physical card it identifies the card itself; on an eSIM it identifies one downloaded profile, so a single eUICC can carry several ICCIDs. It is defined in ITU-T Recommendation E.118 and starts with 89.

ICCID structure

The ICCID follows the issuer-numbering layout of ISO/IEC 7812:

Part	Length	Meaning
Major industry identifier	2 digits	Always 89, for telecommunications
Country code	2–3 digits	Based on the ITU-T E.164 country calling code, e.g. 44 for the UK
Issuer identifier	1–4 digits	Identifies the issuing operator
Individual account number	Variable	Assigned by the issuer
Check digit	1 digit	Calculated with the Luhn algorithm

E.118 limits the ICCID to 19 digits including the check digit, but many issuers use 20 digits — a legacy of early GSM specifications, which treated the ICCID as an opaque 10-byte field. Systems that store or validate ICCIDs should accept both lengths. Some tools display a trailing F when a 19-digit value is padded to fill the 10-byte field.

Where the ICCID is used

• Inventory and logistics: operators and IoT providers track SIM stock, activation and billing by ICCID.
• eSIM provisioning: the SM-DP+ assigns an ICCID to each profile it prepares, and the device uses it to refer to that profile when enabling, disabling or deleting it.
• Device diagnostics: cellular modules report the ICCID of the active profile through AT commands (for example AT+QCCID on Quectel modules), which confirms which subscription is actually in use.

ICCID vs. EID, IMSI and MSISDN

The EID names the chip, the ICCID names the SIM or profile, the IMSI identifies the subscriber to the network, and the MSISDN is the number people dial. The network authenticates the IMSI during registration; the ICCID is not part of that exchange.

Why it matters for testing

When a result looks wrong, the first question is often “which profile was actually active?” Comparing the ICCID the modem reports with the profile you meant to test catches swapped SIMs, failed profile switches and inventory mix-ups. SimCheck.ai keeps each eSIM profile in an inventory with its status and the site and modem it is installed on, so results trace back to the exact profile under test — see eSIM testing.