Registering as a business as new FBA seller using retail arbitrage

If you’re earning more than £1,000 from self-employment then you need to register with HMRC as self-employed: https://www.gov.uk/set-up-sole-trader I think Amazon might need a UTR anyway so it’s worth doing.

If you form a company with Companies House then it would be a company, if not then you’re acting as a sole trader. (side note: Amazon sometimes use the word “company” to mean “companies and sole-traders”, which isn’t helpful)

The main difference from Amazon’s point of view is the verification process. You’ll need to provide a lot more documents if you’re a limited company.

From your point of view, if you’re a company you are not usually personally liable if something goes wrong (unless you’ve acted negligently or with malicious intent), you’ll have a lot more paperwork to do and the company will need to pay corporation tax, then after you receive payments from your company you’ll then need to pay income tax on these and if you’re classed as an employee probably NI too. If you sell the shares in the company you’ll probably need to pay capital gains tax.

As a sole-trader you’d just have income tax and NI to pay, and a tax return. If your turnover is less than £85k you can fill in a simplified tax return (Business details, total income, total expenses, and that’s about it)