How to calculate import duty on goods formulas, examples and a checking workflow.

Import duty is the tax applied to goods imported into Vietnam. It is generally determined from the dutiable value of the goods and the duty rate that corresponds to the HS code.

In practice, businesses calculate import duty when bringing in goods for resale, raw materials for production, machinery and equipment, sample goods, or when budgeting a shipment before signing a contract.

The key point is that import duty does not stand alone. It is usually tied directly to import VAT, special consumption tax, environmental protection tax, or trade-defence duty if the item falls under those regimes.

The HS code is the basis for determining tax policy and goods-management policy. Two items with the same name may carry different HS codes if their nature, function, material or construction differ. When the HS code changes, the import duty rate and related taxes can change too.

For example, an industrial electronic device and a household electronic device can look quite similar on an invoice, but if their function and technical specifications differ, the HS code groups may not be the same.

This is why businesses should not look up an HS code from a generic product name alone. Before calculating tax, clarify the key attributes of the goods.

Before calculating tax, clarify the following:

The General Department of Customs provides a tariff-lookup system and an import/export catalogue database — a source to verify when determining the duty rate by HS code.

For most goods taxed on an ad valorem (percentage) basis, the basic import-duty formula is:

Where:

Many practitioner references present the formula the same way: import duty equals the dutiable value multiplied by the duty rate.

The easy mistake, however, is this: the “dutiable value” is not always simply the price stated on the invoice.

The dutiable value is the part businesses must scrutinise most carefully before applying the formula. In practice, newcomers to trade often take the invoice price straight away to calculate tax. That can be correct in some cases, but it should not be treated as a fixed rule.

If the contract is on FOB terms, the invoice price usually excludes international freight and insurance. In that case, the business must add the necessary amounts to establish the dutiable value at the import border gate.

If the contract is on CIF terms, the price already includes cost, insurance and freight to the port of import. Many guides therefore use CIF as a simple proxy for the dutiable value. Even so, the business still needs to check additional amounts to be added or adjusted based on the actual shipment file.

A practical check is to cross-reference the document set, including:

• Commercial invoice
• Packing list
• Sales contract
• Bill of lading or airway bill
• Insurance (if any)
• Freight documents
• C/O if you want a preferential rate
• Catalogue, technical documents or product photos

Import duty rates are usually looked up by HS code. Having the HS code, however, is not the end of it: the business must determine which type of rate applies to the shipment.

Under the Law on Export and Import Duties, rates for imported goods comprise preferential rates, special preferential rates and ordinary rates. The special preferential rate applies to goods originating from a country or territory with a special preferential arrangement with Vietnam, while the ordinary rate applies to goods that do not fall into the preferential cases.

A simple way to understand it:

After calculating import duty, the business must compute import VAT if the item is subject to VAT.

The commonly used formula is:

The VAT taxable price of imported goods generally comprises the dutiable value, the import duty and any other applicable taxes.

It can be expressed as a practical formula:

Then:

Government Decree 181/2025/ND-CP details the implementation of several articles of the Law on Value-Added Tax and takes effect on 01/07/2025. When updating tax calculations, businesses should check the current legal documents to avoid relying on outdated formulas or interpretations.

The point to remember is that import VAT is not computed on the original price of the goods alone. In many cases, VAT is computed on the price after import duty has been added. So when import duty changes, VAT can change with it.

It is wrong to call every payable amount “import duty”. In practice, the total a business pays for a shipment can comprise several different items.

The general formula can be understood as:

Not every item carries all of these taxes. A shipment of ordinary components, for example, may incur only import duty and VAT. But certain items — cars, alcohol, fuel or goods under a dedicated management policy — can additionally incur special consumption tax, environmental protection tax or additional duty.

Suppose a business imports a shipment with the following details:

Summary table:

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Suppose the same shipment has a dutiable value of VND 100,000,000, but consider two cases:

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In this example, the C/O cuts the total tax payable by VND 11,000,000. The real figure can be far larger for high-value shipments or for frequent imports.

However, having a C/O does not guarantee a tax reduction. The business must check the C/O form, the country of origin, the rules of origin, the HS code, the goods description and the corresponding trade agreement.

In practice, businesses should run a checking workflow before declaring, rather than calculating tax only at the last step. A clear process reduces errors, makes internal cross-checking easier and is more convenient if an explanation is later required.

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Below are mistakes that come up fairly often when calculating import tax:

For businesses importing many items, manual lookups across Excel files, scattered websites and email data are prone to confusion. Each staff member may keep a different version, use different product descriptions or apply inconsistent lookup sources.

Gexim.ai helps businesses build a clearer workflow for checking HS codes and calculating import duty.

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Reduce the risk of scattered data

In many businesses, goods information sits in many places: procurement holds the invoice, logistics holds the bill of lading, accounting holds the tax spreadsheet, and sales only cares about the final cost of goods. When data is scattered, tax calculation and landed-cost checks easily go off.

Gexim.ai pulls the process into one more unified flow — from goods description to HS code, duty rate and tax estimation. This does not fully replace customs expertise, but it lets the team work faster, more systematically and with easier re-checking.

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Calculating import duty looks simple at first glance, but in practice it depends on many factors: the HS code, the dutiable value, origin, C/O, VAT and any additional taxes.

If a business calculates by formula alone without carefully checking the input data, the tax figure can be wrong from the very first step. Conversely, with a clear process — from describing the goods, determining the HS code, looking up rates, computing VAT and archiving the checking basis — the business is far better prepared when planning import costs.

Gexim.ai is built to help trading businesses handle these steps more systematically. From standardising product descriptions and supporting HS code lookup to checking import duty, Gexim.ai reduces manual effort and curbs the risk of scattered data in the import process.