How to Calculate Import Duty: A Step-by-Step Worked Example

Duty Calculation Isn't as Complicated as It Looks

Many new importers dread customs duties because the system seems opaque. In reality, duty calculation follows a straightforward formula. Once you understand the components, you can estimate your duty costs before placing an order.

The Basic Formula

Import Duty = Customs Value × Duty Rate

That's it. Two numbers multiplied together. The complexity comes from understanding what those two numbers actually are.

Step 1: Find Your HS Code

Every product in international trade has a Harmonised System (HS) code — a standardised classification number used worldwide. The first six digits are universal; additional digits vary by country.

How to find your HS code:

• Use the free HS code lookup tool to search by product description
• Check your supplier's commercial invoice (they often include it)
• Search your country's tariff database directly

Example: A portable Bluetooth speaker is classified under HS code 8518.22 (loudspeakers mounted in an enclosure).

Step 2: Determine the Duty Rate

Once you have the HS code, look up the applicable duty rate for your country:

• UK: Check the UK Global Tariff on GOV.UK
• EU: Check the TARIC database
• US: Check the Harmonised Tariff Schedule (HTS)

Example: For HS 8518.22 imported into the UK, the duty rate is 2.0%.

Duty rates also depend on the country of origin. Trade agreements may provide preferential (lower) rates. For example:

• Products from countries with free trade agreements may qualify for 0% duty
• Products subject to anti-dumping measures may face additional duties

Step 3: Calculate the Customs Value

The customs value is the basis on which duty is calculated. The method varies:

CIF-based countries (UK, EU, most countries)

Customs value = Product cost + Freight + Insurance

FOB-based countries (US, Australia)

Customs value = Product cost only (freight is excluded)

Example (UK import):

• Product cost (FOB): $3,500
• Freight to UK port: $800
• Insurance: $35
• Customs value: $4,335

Step 4: Calculate the Duty

Duty = Customs value × Duty rate

Example: $4,335 × 2.0% = $86.70

That's the duty on this shipment. Divided by 1,000 units, that's just $0.087 per unit.

Step 5: Calculate Import VAT/Tax (Where Applicable)

In most countries, import VAT or GST is calculated on:

VAT base = Customs value + Duty

Example (UK, 20% VAT):

• VAT base: $4,335 + $86.70 = $4,421.70
• VAT: $4,421.70 × 20% = $884.34

If you're VAT-registered, this is reclaimable — but it's still cash you need upfront.

Complete Worked Example

Let's put it all together for 500 yoga mats imported from China to the UK:

Per unit: $4,000 product + $600 freight + $40 insurance + $125.28 duty + $953.06 VAT = $5,718.34 total ÷ 500 units = $11.44 landed cost per unit

The supplier quoted $8.00 per unit. The true cost is $11.44 — a 43% increase.

Use the import calculator or LandedCost.io's duty and tax engine to run these calculations automatically for every product in your shipments.

Common Mistakes to Avoid

1. Wrong HS code — misclassification can mean paying too much or too little duty (both cause problems)
2. Forgetting to add freight to customs value — in CIF countries, this undervalues your goods
3. Ignoring preferential rates — if your supplier's country has a trade agreement, you may qualify for reduced rates
4. Not accounting for anti-dumping duties — these are additional to standard duty rates and can be substantial

Getting Help

If you're unsure about your HS code or duty rate, a customs broker can help. Most charge a flat fee for classification advice. Getting it right from the start saves money and prevents delays at the border.