Post-Brexit Rules of Origin: How They Shape Which EVs Are Built in Britain

The invisible rule that shapes British car-making

Most people have never heard of "rules of origin." Yet this single, technical piece of the post-Brexit trade settlement does more to determine where EVs are built in Britain — and whether they're built here at all — than almost any headline policy.

Here's the core of it: under the UK-EU Trade and Cooperation Agreement (TCA), cars traded between Britain and the EU are tariff-free only if enough of the car is made in the UK or the EU. Miss that threshold, and the car faces a 10% tariff crossing the Channel — in either direction.

For an industry where the UK and EU are each other's biggest automotive trading partners, that 10% is the difference between viable and unviable. And for EVs specifically, the rule creates a very particular problem.

What "rules of origin" actually means

A trade deal doesn't just say "no tariffs between us." It says "no tariffs on goods that genuinely originate here" — otherwise the deal becomes a backdoor for third-country goods to get in cheaply.

So the TCA sets a local-content threshold: a car must contain a minimum percentage of UK/EU-originating content (by value) to qualify as "originating" and cross tariff-free. Content sourced from outside the UK and EU — from China, Japan, Korea, the US — counts against the threshold.

For a conventional car, UK and EU manufacturers can usually meet the threshold, because the European supply chain is deep and mature.

For an EV, the problem is the battery.

Why the battery breaks everything

The battery is the single most expensive component in an EV — often 30–50% of the vehicle's value. And here's the difficulty: most EV batteries, and the cells and raw materials inside them, are made in Asia — China, South Korea, Japan.

A British-assembled EV with an Asian-made battery may have so much non-UK/EU content — because the battery alone is such a huge share of value — that it fails the rules-of-origin threshold and gets hit with the 10% tariff when exported to the EU.

This is the trap: you can assemble the EV in Britain, employ British workers, and still fail to qualify as "British" for trade purposes, because the most valuable part came from Asia.

Why this shapes *where* EVs get built

Follow the logic and you see why rules of origin dictate industrial geography:

1. It pushes battery production to Britain and Europe. The only durable way to meet the threshold is to make the batteries here. That's the entire strategic rationale behind the drive to build UK and EU "gigafactories" — not just industrial pride, but trade necessity. Without local battery production, British EV assembly is structurally disadvantaged.

2. It influences where manufacturers site EV assembly at all. A manufacturer deciding where to build its next EV weighs whether it can meet rules of origin there. If Britain lacks nearby battery supply, the calculation can tip toward building the EV in the EU (closer to battery capacity) or elsewhere — a genuine risk to UK automotive employment.

3. It makes battery supply-chain investment existential, not optional. For British car-making to have an EV future, the battery supply chain has to localise. Rules of origin turn "would be nice" into "must happen."

The phase-in that bought time

Recognising that neither the UK nor the EU could localise battery production overnight, the TCA's rules of origin for EVs and batteries were designed to tighten in stages — starting more lenient and stepping up over time, to give the industry a runway to build local battery capacity.

That phasing has been the subject of intense negotiation and at least one high-profile delay, precisely because the battery supply chain hasn't scaled as fast as the original timetable assumed. The tension is permanent: tighten too fast and you tariff an industry that hasn't had time to localise; tighten too slow and you never create the incentive to localise at all.

What this means beyond the factory gate

For British automotive jobs: rules of origin are, quietly, one of the biggest factors in whether EV manufacturing has a future in Britain. Get the battery supply chain built in time, and UK plants can produce qualifying EVs and keep the jobs. Fail, and assembly drifts to where the batteries are.

For the industry's investment decisions: every gigafactory announcement, every battery-plant investment, is partly a rules-of-origin story — a bet on being able to meet the threshold and sell tariff-free into the EU.

For car buyers, indirectly: if British EV production is constrained by rules of origin, that affects model availability, pricing and choice in UK showrooms over the coming years.

The honest assessment

Rules of origin are dry, technical, and almost never make the news. They're also one of the most consequential forces shaping the British car industry's transition to electric.

The uncomfortable truth is that Britain's EV manufacturing future depends heavily on building a battery supply chain fast enough to satisfy a threshold that gets harder over time. The phasing bought a runway. Whether the UK builds the gigafactory capacity to use that runway — before the rules tighten to the point of biting — is one of the defining industrial questions of the decade.

It's not a story with a settled ending. It's a race between a tightening threshold and a scaling supply chain. For anyone who cares about whether cars are still built in Britain in 2035, it's the race that matters most.

• Under the UK-EU TCA, cars trade tariff-free only if they meet a UK/EU local-content threshold — otherwise a 10% tariff applies
• For EVs, the battery (30–50% of value) is the problem: most batteries are Asian-made, counting against the threshold
• A UK-assembled EV with an Asian battery can fail rules of origin and be tariffed exporting to the EU
• This makes UK/EU battery production (gigafactories) a trade necessity, not just industrial ambition
• The rules phase in over time; Britain's EV manufacturing future depends on scaling local battery supply before they tighten

END OF BATCH 07

Section 2 (Recalls) is complete. Section 3 (Auto Tariffs & Trade) is underway.

Next up (Batch 08): topic 71 (UK–US trade deal, JLR & Mini export quota) completes UK & Europe Trade, then Section 3 continues into India & Global Trade (topics 72+).

Say "next batch" to continue.

Key takeaways

• Under the UK-EU TCA, cars trade tariff-free only if they meet a UK/EU local-content threshold — otherwise a 10% tariff applies
• For EVs, the battery (30–50% of value) is the problem: most batteries are Asian-made, counting against the threshold
• A UK-assembled EV with an Asian battery can fail rules of origin and be tariffed exporting to the EU
• This makes UK/EU battery production (gigafactories) a trade necessity, not just industrial ambition
• The rules phase in over time; Britain's EV manufacturing future depends on scaling local battery supply before they tighten