What are an IMSI and an ICCID?¶

Provider records or a forensic report may contain an IMSI and an ICCID.

Evidential caution: that these numbers are interchangeable or identify the user directly.

What this means¶

An IMSI is an international mobile subscriber identity used by the mobile network to identify the subscription.

An ICCID is the serial number assigned to the physical SIM card or eSIM profile.

They are related but answer different questions. The IMSI identifies the subscription identity used on the network. The ICCID identifies the specific SIM or eSIM profile carrying it.

A SIM replacement may change the ICCID while the telephone number and subscription continue. In some circumstances, provider changes or account changes may also affect the IMSI.

Neither identifier proves who held the device or used the account. Personal attribution still requires device possession, access evidence, location, communications and other corroboration.

Be cautious when records span SIM swaps, replacements, ports or eSIM activations.

Where records disagree, retain the discrepancy and establish whether it reflects timing, replacement, transfer or collection method.

What to check or do next¶

• Preserve both values exactly and record the source, provider and relevant dates.
• Use provider records to establish which IMSI, ICCID, telephone number and account were associated at the relevant time.
• Compare them with device identifiers such as the IMEI to see which handset used the subscription.
• Record the source of each identifier and preserve the original records so the relationship can be tested later.