We import a piece of machinery from the US however the US tariff code is different to the UK code, as are duty rates, and the US code does not exist in the UK dataset. Should the exporter list the US code or the UK code as the UK is the country in which we will pay duty.
The UK tariff and duty rate will be used for clearance in the UK. Specific commodity codes on the US tariff will be different to ours, however the first four digits should hypothetically be the same, so if you look under that chapter on the UK tariff you should be able to find an appropriate code.
Ideally the UK code should be listed by the exporter to help the UK clearing agent out, but there might be a US requirement to provide a US code as well.
Basically, the first 6 digits of the tariff code are harmonized and should apply worldwide.
Everything beyond the 6th digit is up to national legislation (for UK: currently EU customs tariff applies), thus national codes may differ.
As the importer/declarant is responsible for stating the correct tariff code, any information provided by the supplier may help in finding the right code, but connot necessarily be relied on…