Importing a package from the US

Hi, My friend from US sent me a package and he brought $10,000 inside the package. Why the delivery company said this amount is not allowed in the UK and said the customs demand a fee to release the package. Can you explain this to me? Thank you

Hi,
When you send gifts to someone in the UK you may need to pay Import VAT and Customs Duty depending on the value of the items.
Please see below link for more information:
Import VAT and Customs Duty on gifts
Thank you.