The Auto Tariff Paperwork That Stops Working on December 1

If you make parts in Canada and they end up in a vehicle crossing into the United States, there is a filing deadline coming that is not yours to make. It belongs to your customer. Your numbers go into it, and if they arrive late, the cost shows up on the vehicle you supply.

Here is how it works, in plain terms.

The 25 percent, and the way around part of it

A vehicle built in Canada or Mexico pays a 25 percent tariff entering the United States. That comes from Proclamation 10908.

If the vehicle qualifies under CUSMA, the importer can have that 25 percent charged only on the parts that were not made in America, instead of on the whole vehicle. On a vehicle with real US content, that is a large number.

It does not happen automatically. Someone has to file with the Commerce Department, one model line at a time, and get it approved.

What changed on August 19

Commerce published a notice saying every approval anyone is currently holding stops covering vehicles imported from December 1 onward, "regardless of any expiration date specified in the determination."

That last part is the whole story. Plenty of companies are holding paper that appears to run into 2027. It stops on November 30.

To get a replacement approved in time, Commerce wants the documentation by September 30. That is not a legal deadline. It is Commerce saying how long its queue takes. It is also the only date they have published, so it is the one to work to.

Why the signature matters

The filing is signed personally by the importer's Chief Financial Officer or General Counsel.

If US customs later decides the American content was overstated, the full 25 percent applies to every vehicle in that model line, going back to April 3, 2025.

So an officer is putting their name on a number that can reach back seventeen months. Nobody signs a supplier figure that turns up in late September without the plant and origin detail behind it.

Which is why, if you supply into someone else's filing, your real deadline sits weeks ahead of September 30. It is whenever that officer is comfortable signing what you sent.

Two things nobody is writing about

Right now your CUSMA-qualifying parts pay no Section 232 tariff at all. That is not a permanent rule. Proclamation 10908 suspends it "until such time that the Secretary establishes a process" for taxing only the non-American content of parts. Sixteen months later, there is still no process.

The day Commerce publishes one, your landed cost changes. No notice period is written into it, and no negotiation is going to slow it down. Canada suspended talks with Washington on August 21, which means less warning rather than more time.

The second thing is that the offsets softening all this only go to plants in the United States. The import adjustment offset is for manufacturers "assembling automobiles in the United States." Oakville, Alliston, Cambridge, Woodstock, Brampton and Oshawa get none of it, and a separate engine offset works the same way.

You carry the risk on the number. Someone else gets the relief.

About the 50 percent everyone is talking about

The new Section 338 tariffs took effect on August 22 at 50 percent, and they do hit CUSMA goods, which is what makes them different. We wrote about that when the proclamations were signed.

They do not hit vehicles and parts already under Section 232. Proclamation 11048 says its duties do not apply to anything "subject to duties pursuant to section 232," and Holland & Knight points out that none of its 439 lines is even in the vehicles chapter. The 50 percent is on furniture, cement, wood, clothing and food.

One caution. The exemption follows the product, not the industry. Packaging, tooling and odd sub-components that are not on the Section 232 lists do not get it, so a bill of materials treated as uniformly clean is where a surprise duty turns up.

Where Mexico comes in

The benefit counts American content. It does not care whether the rest of the vehicle was built in Ontario or in Guanajuato. The notice treats vehicles "imported from Mexico and Canada" identically.

What differs is who is in the room. The next round of talks on automotive content rules is between the United States and Mexico, in Washington in September, and one of the proposals on the table would lift the regional content requirement to 82 percent, which we covered here.

Mexico has held that seat since May and used it. If your footprint already spans the corridor, that is worth something concrete: a company you own in Mexico sits inside the conversation where next year's content rules get set, with the state and federal counterparts who carry it.

What to do this week

Ask your customer what their approval covers after November 30. The answer is nothing, whatever it says on the paper.

Then ask what date they need your content data by. And ask yourself whether you can actually pull plant and origin detail off your own bill of materials on short notice, because that question usually takes longer to answer than people expect.

Calder & Vale advises Canadian and US companies entering and operating in Mexico on entity structure, on site and incentives through direct relationships with the state economic development ministries, and on customs and origin exposure.