Last reviewed: May 2026
Import Cost Guide uses official and user-entered data to estimate import duty, import VAT and landed cost for goods imported into the United Kingdom.
This page explains the data sources currently used by our calculators, what each source is used for, how recently retrieved data is handled, and where users should verify final import decisions.
Primary data source
GOV.UK Trade Tariff
The main official source used by the UK Import Duty & Landed Cost Calculator is the GOV.UK Trade Tariff.
The GOV.UK Trade Tariff can be used to look up commodity codes, duty rates, VAT treatment, suspensions, reductions and other tariff-related information for goods imported into or exported from the United Kingdom.
Official source:
Official tariff API
When a user enters a supported 10-digit commodity code, Import Cost Guide can try to retrieve structured tariff data from the GOV.UK Trade Tariff API.
The API may provide structured information such as:
- Commodity code details
- Commodity descriptions
- Duty measures
- VAT measures
- Import or export controls
- Other tariff measures linked to the commodity code
Official API information:
How tariff data is used
When official tariff data can be retrieved and a simple duty or VAT rate can be detected, the calculator may use that rate in the estimate.
If official tariff data cannot be loaded, or if the relevant tariff measures are too complex to safely reduce to a simple percentage rate, the calculator uses the duty and VAT rates entered in the form.
This means the calculator can still be useful even when official data is unavailable or when additional verification is needed.
Recently retrieved tariff data
Official tariff responses may be stored for up to 24 hours.
This helps:
- Make repeat calculations faster
- Reduce unnecessary requests to official sources
- Keep calculations usable if the same commodity code is checked multiple times
- Allow the calculator to show when data was last retrieved
If recently retrieved tariff data is available, the calculator may use it instead of requesting the same data again immediately. If the stored data has expired, the calculator may try to refresh it from the official source.
User-entered data
Some inputs are entered directly by the user. These are treated as editable assumptions, not official data.
User-entered inputs may include:
- Product value
- Shipping cost
- Insurance cost
- Other import costs
- Broker, courier or handling fee
- Number of units
- Selling price per unit
- Exchange rate to GBP
- Duty rate, when official tariff data is not used
- VAT rate, when official tariff data is not used
The accuracy of the estimate depends partly on the accuracy of these user-entered assumptions.
Commodity codes
The commodity code entered by the user is a critical input. A different commodity code can lead to a different duty rate, VAT treatment, control requirement or additional tariff measure.
The product description field is for reference only. It does not automatically classify the goods. The official tariff lookup is based on the commodity code entered in the calculator.
Before relying on an estimate for a commercial shipment, users should verify that the commodity code matches the exact goods being imported.
Data this calculator does not fully handle yet
The current calculator is designed as a practical landed cost estimator. It does not fully resolve every possible customs scenario.
Examples of data or rules that may require separate verification include:
- Anti-dumping duties
- Safeguards and trade remedies
- Tariff quotas
- Suspensions or conditional reductions
- Preferential origin treatment
- Rules of origin
- Excise duties for alcohol, tobacco or fuel
- Product-specific controls, licences or certificates
- Special Northern Ireland or non-standard import scenarios
- Courier, broker, inspection, storage or clearance fees not entered by the user
Exchange rates
The calculator currently uses the exchange rate entered by the user.
For GBP calculations, the exchange rate is 1. For EUR, USD or other supported currencies, users should enter the exchange rate to GBP they want to use for the estimate.
Future versions may add official or regularly updated exchange-rate data. Until then, exchange rates are treated as editable assumptions.
Calculation logs
Import Cost Guide may store anonymous calculation logs to improve the calculator, detect common use cases and understand which commodity codes or import scenarios users are testing.
Calculation logs are intended to help improve the tool and future content. They should not include unnecessary personal data.
Stored calculation data may include:
- Origin country
- Destination country
- Commodity code entered
- Product value
- Shipping and insurance values
- Duty and VAT rates used
- Estimated landed cost
- Whether official tariff data, recently retrieved tariff data or entered rates were used
How source information is shown to users
When a calculation uses official or recently retrieved tariff data, the calculator may show a source block explaining:
- The commodity code used
- The data source
- Whether the duty rate came from official tariff data or entered rates
- Whether the VAT rate came from official tariff data or entered rates
- When the data was last checked
- Whether additional tariff checks are recommended
This source block is designed to make assumptions visible instead of hiding how the estimate was produced.
Why official data may still need verification
Official tariff data can include measures that are not simple percentage rates. Some measures may depend on product details, origin, conditions, quotas, licences or non-percentage duties.
For this reason, a calculator estimate should not be treated as a final customs decision. Users should check the official tariff page and seek professional advice where needed before importing.
Corrections and source updates
Import Cost Guide aims to make sources and assumptions clear. If you believe a source, formula or explanation should be corrected, please contact us through the contact page.
As the project develops, this page may be updated to include additional countries, additional official sources, exchange-rate sources, product-category mappings and improved tariff handling.