Calculation methodology

How the import estimate is worked out

The estimator separates value, base duty, conditional measures and import tax. It shows a component only when the available inputs can support the calculation.

Method reviewed 5 August 2026.

Planning formula

Customs value = goods value + included transport and insurance adjustments.

Ad valorem duty = customs value × selected duty rate.

Import VAT or GST = destination tax rate × the destination’s taxable import base.

Estimated landed amount = entered costs + calculated duty + calculated tax + covered extra measures.

1. Validate the inputs

The product search is matched to an HS code or national tariff description. The user selects the importing country and may select origin. Goods value, shipping and insurance are entered separately so that the result can explain its value basis.

Product wording is not a customs ruling. If several codes are plausible, the estimate is only as reliable as the selected match. Quantity, weight and composition are not fully captured by the current form.

2. Select the duty source

Use a matching national or regional tariff-line row for the destination.
Use the ordinary or MFN treatment unless a supported preference applies.
Use WTO MFN reference data as a labelled fallback when no usable national row exists.
Keep a missing or conditional rate visible instead of silently converting it to zero.

Specific and compound rates can depend on weight, quantity, alcohol content or another unit. The calculator only prices them when the required amount and unit can be supported. Otherwise the legal rate is shown as a check.

3. Test preferences and extra measures

A preferential rate is conditional on rules of origin and evidence. It is not inferred from the shipping country alone. Additional duties are applied only where imported coverage identifies the measure and its product and route conditions.

Coverage of trade remedies, quotas, safeguards and suspensions is incomplete. A result can therefore be useful for base-duty planning while still requiring a separate measure check in the official tariff.

4. Calculate VAT or GST

The estimator uses an imported standard or broad import-tax rate where available. A common base is customs value plus duty, but national rules can add freight, insurance, excise and other incidental expenses. The US model records that there is no federal import VAT or GST; it does not attempt state sales-tax calculation.

Product-level reduced, zero and exempt mapping is incomplete. The result labels this gap rather than presenting a standard rate as a confirmed product treatment.

5. Preserve source context

Runtime rows carry source identifiers and available raw-file provenance. Calculator results expose the source name, tariff family, reference period and important caveats. The public source register links to the relevant authorities.

How to interpret the result

National row: Best available base-rate input, still subject to classification and legal notes.
WTO fallback: Planning reference used because a national row was unavailable.
Conditional: A possible charge or relief that needs facts or documents not entered.
Not priced: A known component that must be added outside the displayed total.