After Brexit

 UKCA Marking and CE Marking

 https://www.gov.uk/guidance/using-the-ukca-marking#when-to-use-the-ukca-marking

VAT

https://www.gov.uk/guidance/vat-and-overseas-goods-sold-directly-to-customers-in-the-uk

VAT When to register

https://www.gov.uk/vat-registration/when-to-register

• Businesses outside the UK
• There’s no threshold if neither you nor your business is based in the UK. You must register as soon as you supply any goods and services to the UK (or if you expect to in the next 30 days).

NETPS - Non-established-taxable-persons
https://www.gov.uk/government/publications/vat-notice-7001-should-i-be-registered-for-vat/vat-notice-7001-should-i-be-registered-for-vat#non-established-taxable-persons-netps-basic-information

VAT and overseas goods sold directly to customers in the UK

https://www.gov.uk/guidance/vat-and-overseas-goods-sold-directly-to-customers-in-the-uk#goods-that-are-outside-the-uk-at-the-point-of-sale

Business to business sales to UK VAT-registered customers

The seller will not need to charge and account for VAT if the customer gives them their VAT registration number.

Goods exported from the UK from 1 January 2021 (VAT Notice 703)

https://www.gov.uk/guidance/vat-on-goods-exported-from-the-uk-notice-703