Type Allocation Code part of an IMEI

Description

The Type Allocation Code (TAC) is the foundational component of both the IMEI and IMEI-SV. It constitutes the first eight digits of these identifiers. The TAC itself is not a random number; it is a code officially allocated by a central body (historously by BABT, now by the Global System for Mobile Communications Association's GSMA-led IMEI Allocation Board) to a device manufacturer for a specific device model or a range of models. Therefore, the TAC uniquely identifies the device's brand, model, and often specific variant (e.g., different colors or regional versions).

Operationally, the TAC is the most frequently used part of the IMEI for high-level device identification. When a network receives a full IMEI, it can immediately extract the TAC to determine the device type without needing the unique serial number. This is leveraged in numerous network functions. For instance, radio access network algorithms might apply specific optimization parameters based on the device model identified by the TAC. Core network policy functions can use the TAC to apply device-specific QoS policies or restrictions. It is also the primary key used in device databases and analytics platforms to categorize device populations.

From a regulatory and standards perspective, the TAC is crucial for device type approval. Regulatory bodies use the TAC to track which device models have been certified for operation in their jurisdictions. The TAC is also integral to the IMEI-based device blocking ecosystem. While a full IMEI is needed to block a specific stolen device, a TAC can be used in more broad actions. For example, if a particular device model is found to have a critical, un-patchable radio flaw, regulators or operators could potentially block all devices with that TAC from accessing the network, a process that would utilize the Equipment Identity Register's (EIR) capabilities. The TAC's structure ensures global uniqueness and prevents collisions between different manufacturers' device codes.

Purpose & Motivation

The TAC was established to provide a standardized, hierarchical structure within the IMEI, enabling efficient categorization and identification of device models at scale. Before its formal definition, identifying a device model from its serial number required proprietary manufacturer databases, which was inefficient for network operators and regulators. The TAC solves this by encoding the model information directly into the identifier's structure, allowing for instant recognition.

Its creation was motivated by the needs of regulatory type-approval processes, device market analytics, and network optimization. Regulators needed a reliable code to associate with a device's certification documents. Network operators needed to quickly identify device capabilities (e.g., supported frequency bands, maximum data rates) to optimize radio resource allocation and troubleshoot device-specific issues. The TAC, introduced as a core part of the IMEI and later refined, met these needs by providing a globally unique, operator-readable 'model number' that is consistently reported by every device. This allows for automated systems to apply model-specific configurations and policies across the entire mobile network.