Taxpayers importing goods into the UK have to work out the value of their goods (the “customs value”) to calculate any liability to Customs Duty and import VAT. This value has to be reported even if there is no duty or VAT to pay, or if the goods are entered to a customs warehouse.
The HMRC guidance is given under the following headings:
- Customs Duty
- Importing goods into Northern Ireland
- How to work out the customs value of your imports
- Goods entering or being removed from a customs warehouse
- What to do if you cannot establish the value for Customs Duty
- Evidence and keeping records
- What to do if you disagree with a customs decision
https://www.gov.uk/guidance/prepare-to-work-out-the-customs-value-of-your-imported-goods