Who can register a company in uk?

to become a sole trader, you can in theory open up a business overnight. The only thing you have to do is register as a sole trader with the inland revenue.

I believe you have to be of a certain age...over 16, or maybe 18. If you area foreign national (non-EU) then you must have been granted leave to stay in the UK, unless the conditions of your visa state that you cannot work (eg. fiancee or tourist visas).
Apart from that I think that just about anyone can set up a business here. Register for a VAT number and income tax payments and away you go!

They changed the rules on company formation.
A single person can now form and register a company, so now anybody can.

Any one can register a company in the UK, as long as they are not an undischarged bankrupt or are disqualified by a court from holding a directorship. There are no restrictions on age on being a company director, but Companies House discourages anyone under the age of 16 from being one, as they will probably not understand the legalities of being a company director, (and there are loads!!) If you are based in Scotland, you can't register if you are under 16. Hope this helps x