Why CBP Scrutiny on Vietnam Imports Is About to Increase

March 2026
Asia Agent

For the past few years, Vietnam has been the biggest winner of the China +1 strategy.

Factories expanded.
Exports surged.
Companies moved final assembly out of China.

For many importers, Vietnam became the simple answer to tariffs.

Move production.
Avoid China duties.
Keep the same supply chain running.

But regulators are starting to ask a different question.

Did the supply chain actually move — or just the final step of production?

That question is why CBP scrutiny on Vietnam imports is increasing.

Why Vietnam Became the Center of China+1

When tariffs hit China in 2018, companies needed alternatives quickly.

Vietnam was the most obvious option.

It offered:

Lower labor costs
Established manufacturing clusters
Strong export infrastructure
Proximity to Chinese supply chains

Many companies adopted a simple structure.

Components produced in China.

Final assembly performed in Vietnam.

Product labeled Made in Vietnam.

For some products, this structure is legitimate.

For others, it raises regulatory questions.

The Legal Test: Substantial Transformation

Country of origin is not determined by where the final screw is tightened.

It is determined by something called substantial transformation.

In simple terms, the manufacturing process must create a meaningful change in the product’s:

• name
• character
• or use

If the production process does not meet that threshold, the country of origin may still be considered China.

That means tariffs can still apply — even if the final assembly happens in Vietnam.

Why Regulators Are Paying Attention

Vietnam’s export growth to the United States has been dramatic.

In some industries, export volumes increased faster than the country’s manufacturing capacity.

That raises questions regulators take seriously.

For example:

Factories exporting volumes far beyond their production capacity.

Products requiring components that Vietnam does not manufacture.

Imports of Chinese components that closely match exported finished goods.

These patterns often trigger tariff circumvention investigations.

How CBP Investigates Supply Chains

When CBP investigates a shipment, they often look beyond the invoice.

Typical requests include:

Factory verification.

Bill of materials.

Supplier declarations.

Production capacity verification.

Invoice and payment reconciliation.

Evidence showing where the manufacturing transformation actually occurred.

If the documentation does not match the supply chain, shipments can be detained.

Many companies only discover the problem when CBP sends a CF-28 Request for Information.

At that point, the response clock has already started.

Where This Shows Up in Your Supply Chain

At the factory:

Suppliers may not have documentation proving where inputs come from or how production is structured.

At the forwarder:

Shipping documents may not match supplier declarations or production records.

At customs entry:

Country-of-origin claims may not align with the actual manufacturing process.

At the warehouse:

Detained shipments disrupt inventory planning and force expensive logistics decisions.

The Mistake Many Importers Are Making

Many companies assume that moving assembly to Vietnam automatically solves the tariff problem.

But regulators are looking at the entire supply chain, not just the final production step.

If the documentation cannot prove substantial transformation, the country-of-origin claim may not hold.

And when CBP asks for proof, many importers realize the documentation simply doesn’t exist.

What Importers Should Do Now

Vietnam remains an excellent manufacturing base.

But companies need to treat origin compliance much more seriously.

That means:

Verify factories on the ground.

Understand the bill of materials.

Document the manufacturing process.

Confirm substantial transformation.

Prepare compliance files before shipments leave the factory.

Companies that already have this documentation respond to CBP quickly.

Companies that don’t often discover the problem when the shipment is already at the port.

The Bottom Line

Vietnam will remain a critical part of global manufacturing.

But the era of simple China +1 assembly without documentation is ending.

The new tariff environment is not just about where a product is assembled.

It is about whether the entire supply chain can be proven.

Importers who understand their supply chains will navigate this shift successfully.

Those who don’t may find themselves answering questions from CBP while their containers sit at the port.

FAQ

Q: Is Vietnam facing new tariffs from the United States?
Vietnam itself is not the primary tariff target, but U.S. regulators are increasingly investigating supply chains that may be circumventing China tariffs.

Q: Does assembling products in Vietnam automatically change the country of origin?
No. The production process must meet the substantial transformation standard.

Q: What triggers CBP investigations of Vietnam imports?
Rapid export growth, mismatched production capacity, supplier documentation gaps, and tariff circumvention signals.

Q: How can importers protect themselves?
By verifying factories, documenting production processes, mapping supply chains, and maintaining compliance files before shipments move.