alt Hacker NewsDunno about that. I live in the US. I can start a small business today and the only thing I'd have to do differently is file an additional form on my taxes next year. Yes, that's a simplification that doesn't apply to every situation, but it is still completely accurate.
That's pretty much the situation in the UK if you are a sole trader. If you set up a limited liability company, that's a separate entity and has its own tax reporting requirement, but nothing onerous. I am a sole trader, and manage a small company separately from that.
One thing I have heard of in the USA is the need for a "business licence". I'm not sure what that is or whether it applies to all businesses, so I'm not sure what it would correspond to in the UK. Neither of my businesses needed any licences or permissions to start trading.