What is the difference between IMEI and TAC?

The IMEI (International Mobile Equipment Identity) is a unique 15-digit identifier for every mobile device. The TAC (Type Allocation Code) is the first 8 digits of the IMEI, identifying the device manufacturer and model. While IMEI is unique per device, TAC is shared across all units of the same model.

How do I find the IMEI of my phone?

There are three common methods: dial *#06# on your phone keypad, go to Settings > About Phone > IMEI, or check the SIM tray or the sticker under the battery (older phones). All methods return the same 15-digit IMEI number.

What is the Luhn algorithm used for in IMEI?

The Luhn algorithm validates the 15th digit (check digit) of an IMEI. It detects accidental transcription errors such as transposed or mistyped digits. It does not verify authenticity or whether a device is stolen, only structural validity.

Can I identify a phone model from its IMEI?

Yes. The first 8 digits (TAC) map to a specific manufacturer and model in the GSMA TAC database. A TAC lookup tool can instantly return the brand, model name, and supported technologies from any valid IMEI.

Why do telecom engineers need IMEI and TAC lookup?

Telecom engineers use IMEI/TAC data for drive test device qualification, fleet auditing (verifying supported bands and capabilities), network planning based on device population, and troubleshooting UE-specific issues on live networks.

IMEI & TAC Lookup Guide for Telecom Engineers (2026)

What is an IMEI and Why Check It?

Every mobile device in the world carries a unique 15-digit fingerprint: the IMEI (International Mobile Equipment Identity). Defined by 3GPP in TS 23.003, the IMEI lets operators, engineers, and regulators identify any device on a cellular network without ambiguity.

Checking an IMEI is essential for multiple reasons: verifying a device is not reported stolen, confirming it supports the required frequency bands, identifying the exact model during field troubleshooting, and auditing device fleets before network deployments.

IMEI Number Structure Explained

An IMEI is composed of 15 decimal digits grouped into three functional blocks. Understanding this structure is the foundation of any IMEI lookup.

Segment	Digits	Purpose
TAC	1 – 8	Type Allocation Code — identifies manufacturer and model
Serial	9 – 14	Unique serial number assigned by the manufacturer
Check digit	15	Luhn checksum for error detection

Example: in the IMEI 353911107654321, the first 8 digits are the TAC (Samsung Galaxy S25), the next 6 are the serial, and the last digit is the Luhn check.

3 Ways to Find Your IMEI

Dial *#06# — works on every GSM, UMTS, LTE, and 5G device. The IMEI (or IMEIs for dual-SIM) displays instantly.
Settings > About Phone — navigate to the device information screen. The IMEI is listed alongside the serial number.
SIM tray or packaging — the IMEI is printed on the SIM tray (most modern phones) or on the original box label.

Tip for fleet managers: Use ADB command adb shell service call iphonesubinfo 1 to extract IMEI programmatically during device provisioning.

How IMEI Verification Works

IMEI verification involves two distinct steps: structural validation and database lookup.

Luhn validation checks that the 15th digit is mathematically consistent with the first 14 digits. The algorithm doubles every second digit from the right, sums the resulting digits, and verifies the total is divisible by 10. This catches common typos but does not prove a device is genuine.

TAC database lookup is the second step. The first 8 digits are matched against the GSMA TAC database to return the manufacturer, model, and supported technologies. This is what powers the HiCellTek IMEI checker.

Professional Use Cases

Network engineers

Before a drive test campaign, engineers must qualify test devices: confirm supported bands, carrier aggregation combinations, and VoLTE capability. A TAC lookup instantly reveals whether a device supports Band 28 (700 MHz) or n78 (3.5 GHz 5G NR) without powering it on. During fleet audits, TAC data helps operators understand what device population is active on their network — critical for planning VoNR rollouts or sunsetting 3G.

Device resellers

IMEI verification confirms a device is not blacklisted, matches the advertised model, and has not been tampered with. This is standard practice for certified refurbished marketplaces.

Insurance and compliance

Insurers and regulators use IMEI checks to validate claims, detect fraud, and enforce import regulations. Many countries mandate IMEI registration for every device sold domestically.

What is a TAC Number?

The TAC (Type Allocation Code) is the first 8 digits of an IMEI. It is allocated by the GSMA to device manufacturers when a new model is certified. Each unique TAC maps to exactly one manufacturer-model-variant combination.

For example, a TAC starting with 35391110 identifies a specific Samsung model, while 35407115 points to an Apple iPhone variant. The TAC database contains millions of entries and is continuously updated as new devices enter the market.

Note: Before 2014, the TAC was only 6 digits (with a 2-digit FAC — Final Assembly Code). Since then, the GSMA extended TAC to 8 digits, absorbing the FAC. Legacy documentation may still reference the old format.

TAC lookup is particularly valuable for network planning: by aggregating TAC data from network traces, operators can map the device ecosystem on their network — percentage of 5G-capable handsets, VoLTE-enabled terminals, or devices supporting specific band combinations via API.

IMEI Security: Blacklists, Theft, Counterfeits

The GSMA IMEI Database (formerly CEIR) is a global blacklist shared among operators. When a device is reported stolen, its IMEI is added to the blacklist, and participating operators block it from registering on their networks.

However, IMEI cloning remains a challenge. Counterfeit devices often reuse valid TACs from legitimate models but with fabricated serial numbers. A Luhn check will pass, but cross-referencing multiple data points (TAC + device capabilities + baseband version) can expose inconsistencies. This is why professional tools that go beyond simple IMEI lookup are essential for thorough device verification.

Warning: Changing or reprogramming an IMEI is illegal in most jurisdictions, including the EU, UK, and many African and Middle Eastern countries.

Check Any IMEI for Free

HiCellTek provides a free online IMEI and TAC lookup tool built for telecom professionals. Enter any IMEI or TAC to instantly retrieve the device manufacturer, model name, and supported network technologies.

Whether you need to qualify a device before a drive test, audit a fleet of terminals, or verify a second-hand purchase, our checker delivers accurate results from an up-to-date TAC database.