LOL - you'll need to make a profit in order to worry about taxes. Good luck!
After that, it does get complicated, and as you have found, even HMRC will tell you "it depends".
There's 3 ways that forex (or indeed any other kind of "daytrading") can be classified - gambling, trading or investment.
- If they judge that you are engaged in speculative/gambling activity, profits are free of tax.
- If they judge that you are engaged in a business activity, you will be taxed like a business. I.e. based on what income you generate, but with the ability to offset profits with costs e.g. computers, subscriptions etc. (Or - you'll be able to use your forex trading losses to offset profits you make in another business :-) )
- If they judge that you are engaged in investment, you will be taxed like a private investor i.e. CGT rules apply.
There are no hard and fast rules - HMRC look at the pattern of your trading, why you bought and sold things, how long you owned them for, how often you trade, how many trades you make etc etc. To some extent, the instrument used makes a difference - a spreadbetting account is more likely to be treated as gambling than holding currency reserves, for example.
Important thing is to keep good records of everything and get proper advice if you actually look like you need to worry about tax.