Amazon.co.uk and Amazon.com are the same platform in principle, but the selling experience differs in several important ways. Understanding these differences matters whether you are deciding which marketplace to focus on or considering expanding from UK to US selling.
Market Size and Competition
The US marketplace is roughly five to seven times larger than the UK by revenue. More customers means more sales potential, but it also means more competition. Many product categories on Amazon.com are significantly more competitive than the same categories on Amazon.co.uk, with more sellers, more advertising spend, and more established brands fighting for visibility.
The UK marketplace is smaller but often less saturated. Products that have dozens of competing sellers on the US marketplace may only have a handful on the UK site. For many sellers, this lower competition makes the UK a more practical starting point.
Fee Differences
Referral fee percentages are generally similar across both marketplaces, but FBA fulfilment fees and storage fees differ. The US uses a different size tier system and different fee amounts. Currency conversion also plays a role — when calculating profitability for US sales as a UK-based seller, you need to account for exchange rate fluctuations and Amazon's currency conversion fees.
Customer Behaviour
UK and US customers have different buying patterns. Return rates tend to be slightly lower in the UK. Average order values can differ by category. Seasonal patterns vary — the UK does not have Thanksgiving, so Black Friday demand builds differently. Product preferences can differ significantly — bestsellers in one marketplace are not automatically bestsellers in the other.
Logistics and Compliance
Selling from the UK on Amazon.com means international shipping, customs duties, US sales tax obligations, and potentially different product compliance standards (UL certification for electronics, FDA requirements for cosmetics, etc.). These add complexity and cost that eat into your margins.
Most UK sellers are best served by building a strong Amazon.co.uk business first. The UK marketplace has plenty of opportunity, the logistics are simpler, the compliance requirements are familiar, and you keep full control of your cash flow without currency conversion. Expansion to the US is a natural next step once your UK business is established and generating consistent profit.