What a tier 1 supplier is, and where the tier labels break down

A tier 1 supplier is a company that sells parts, modules or systems directly to a vehicle manufacturer, while tier 2 and tier 3 suppliers sit further back and sell to the tier above them. The labels are a convenient shorthand for buying, quality and risk teams, but they describe a contractual relationship for a given part, not a fixed property of a company.

This explainer sets out what each tier usually covers, which responsibilities tend to sit where, how quality standards and customer requirements travel down the chain, and why software, electronics and batteries are making the boundaries harder to read. It is written for purchasing, supplier quality and programme teams at manufacturers and suppliers in the UK.

What a tier 1 supplier does

The tier 1 holds the purchase order from the vehicle maker and delivers to its plant. In many programmes it also carries design responsibility for the system it supplies, runs product and process validation, submits production part approval, manages delivery schedules into the assembly line and handles warranty claims linked to its parts.

That direct position also makes it responsible for its own sub-suppliers. A vehicle maker generally expects the tier 1 to select, approve, monitor and develop the companies that feed it, and to answer for their failures. The tier 1 is therefore both a supplier and a buyer, and much of its value lies in managing the chain behind it.

Tier 2 and tier 3

A tier 2 supplier makes components or sub-assemblies that a tier 1 incorporates into its product. A tier 3 supplier typically provides raw or semi-processed materials and basic parts to tier 2 companies. Below that, the chain extends to refiners, chemical producers and miners, which are rarely named in automotive contracts but can still stop a production line.

Typical categories by tier

The table below is illustrative. The same product can sit at different tiers depending on who buys it and how it is integrated.

For example, a regional machining company might supply brackets to a seat maker, which makes it a tier 2 for that part, while selling a different machined part straight to a vehicle plant, where it acts as a tier 1. Supplier databases that tag a company with a single tier will miss that distinction.

How quality requirements flow down the tiers

Most vehicle makers expect their production suppliers to work to IATF 16949, the automotive quality management standard. The IATF describes the 2016 edition as replacing ISO/TS 16949:2009 and as an effort to harmonise assessment and certification across the automotive supply chain. A revision towards a second edition was announced in October 2024 and was still in progress in November 2026, according to the IATF’s own communiqués.

The IATF’s June 2026 FAQs clarify two points that matter for tiers:

• A tier 2 organisation must consider the customer requirements of its direct customers, not those of vehicle makers it does not supply directly. Requirements reach tier 2 through the tier 1, not around it.
• Supplier certification status is one criterion in deciding whether a second-party audit of a supplier is needed, so certification is evidence in a risk assessment rather than an automatic pass.

On top of the standard, many vehicle makers publish customer-specific requirements, and the IATF lists documents from several manufacturers. A tier 1 has to translate those requirements into its own purchasing terms, which is why sub-tier quality often depends on how well the tier 1 does that translation.

Why the tier 1 supplier label is blurring

Software and electronics

In a conventional model, the tier 1 that supplies an electronic control unit also supplies its software. That is no longer a safe assumption. A vehicle maker may write some software itself, buy it in from a specialist, or require a tier 1 to integrate code from a company it has chosen. The hardware and software for one module can then come from different tiers.

Regulation has followed the risk. Under UN Regulation No 155 on cyber security, published in the EU Official Journal on 9 March 2021, the manufacturer’s cyber security management system must show how it manages dependencies on contracted suppliers and service providers, and must identify and manage supplier-related risks for each vehicle type. The duty sits with the manufacturer whatever tier the code came from. The IATF FAQs add that embedded software development should receive the same rigour as hardware, pointing to Automotive SPICE and CMMI as assessment approaches. Our piece on the software delivery package procurement should ask for covers the acceptance side.

Batteries and materials

Electrification has pulled companies that once sat deep in the chain closer to the vehicle maker. Some manufacturers contract directly with cell producers or materials suppliers, bypassing the traditional tier 1 pack integrator, or take pack assembly in-house. That turns a would-be tier 2 or tier 3 into a direct supplier for strategic reasons.

Regulation pushes in the same direction. The EU Batteries Regulation 2023/1542, adopted on 12 July 2023, expects economic operators placing batteries on the EU market to set up battery due diligence policies and introduces a digital battery passport, both of which need information from far up the chain. UK government support recognises the same structure: the DRIVE35 Transformation pillar lists batteries, electric motors and drives, power electronics, upstream supply chain and recycling within its scope.

Using tier labels without being misled

Tier labels remain useful for organising purchasing and supplier quality work. The risk lies in treating them as a map of exposure. The SMMT lists component and materials shortages, high energy costs and geopolitical events among the pressures on automotive supply chains, and those pressures usually start below tier 1.

Three practical habits help:

1. Record tier per part and per customer relationship, not per company.
2. Record who chose each sub-supplier, because a sub-supplier chosen by the vehicle maker but bought through a tier 1 changes who can act when it fails.
3. Track software, data and service suppliers alongside hardware, since they may not appear in a parts-based tier list at all.

Our analysis of supplier risk below tier one sets out why disruption often starts deeper in the chain, and the guide to mapping lower-tier supplier dependencies explains how to build the evidence.

Key points for purchasing and supplier quality teams

• A tier 1 supplier contracts directly with the vehicle maker and usually manages the tiers behind it.
• Tier is a relationship for a specific part, so one company can be tier 1 and tier 2 at once.
• Under IATF guidance, requirements reach tier 2 through its direct customer, which makes flow-down quality a tier 1 task.
• Software and battery sourcing increasingly bypass the traditional sequence, while cyber security and battery rules keep responsibility with the manufacturer or the business placing the product on the market.
• Record tier, sourcing decision and software suppliers per part to see real exposure.

Sources

• IATF Global Oversight: About IATF 16949:2016
• IATF Global Oversight: IATF 16949 FAQs (June 2026)
• IATF Global Oversight: home page and communiqués
• EUR-Lex: UN Regulation No 155, cyber security and cyber security management system
• EUR-Lex: Regulation (EU) 2023/1542 concerning batteries and waste batteries
• GOV.UK: DRIVE35 Funding Programme: Transformation
• SMMT: Supply chain

Sources checked in November 2026. Rules, rates and schemes can change after publication, so check the linked official pages before acting.