I understand. It's tricky because the UK just changed their rules January 1, 2021:
-If your sale is below £135 GBP:
Your U.S. company needs to start charging VAT to your UK customers. Yes, that is right for any product priced £1- £135 GBP you need to add 20% UK VAT. This means a non-UK resident seller must add 20% VAT on the sale though their website checkout. For example, if you are selling something for $10 you need to add $2 VAT and thereby the total charge is $12 at checkout. The $2 collected in VAT needs to be reported and paid into HMRC. In addition, a simplified customs declaration will still be required. Charging VAT in the UK and reporting - requires a UK VAT registration. Email me at firstname.lastname@example.org we are happy to explain more.
-If your sale is above £135 GBP:
Goods above this value are subject to import VAT and duty at customs. No new change to this rule, but the tricky part now becomes to keep track of currency exchange rates at each time of sale. For example, if your product price is $180 USD some days you might be above £135 GBP and other days below. The £135 threshold is based on the intrinsic value of the goods, excluding transport, insurance and other import taxes.
If your imported goods are valued above £135 (or multiple goods with a combined intrinsic value above £135) then you as a U.S. seller still have the option to make your customers pay for VAT to customs. In other words, when you sell the product you inform your customer that they are responsible for importing the goods and have to pay duty + 20% VAT to customs.