In reply to chers: While I sympathise with the plain English issues and the tax people not doing what you wanted (most people, for small amounts would rather their tax code was changed as that acts like a monthly payment plan in the months ahead to pay tax on income already received... unless people are organised and keep money back to pay a tax bill the thought of being billed and writting a cheque can be painfull) people seem to loose sight of the fact that we are obliged legally and morally to pay our legal taxes.
Figuring out precisely what your legal tax is can be complex but in most cases is pretty simple. I self asses annualy some simple bits and pieces and it is not a painfull process. I have also had periods when I have had PAYE emploment and untaxed consultancy work that I declared, and calculated a profit on by deducting expenses etc and paid tax on the remainder. Again, relatively easy. A tax payers obligation is to declare their situation honestly, the tax mans job is help you pay the correct tax. Its not the tax mans job to guess your situation as you are required to asses yourself to them.
There are pretty good guides out there, links to which have been supplied. Outside those guides most of the rest of the discussion here (my comments included) are second hand, largely amateur interpretations of varying quality.
As an aside - how many on this thread would walk into a shop, pick up a £500 item and walk out? Yet theres a number of comments around if they don't find/catch me...... Total red herring - whats the relevance of discussing 'how' the authorities will catch you if you don't do it properly. They might or might not but if anybody on this thread deliberately sets out to not pay tax in hopes they will not be noticed thats theft.
While I'd love to see tax simplified as I believe we waste an enormous amount of money either calculating it, collecting it or figuring out schemes to 'minimise' it I'd also love everybody to pay the correct amount so the country has more income to distribute.
General rants not directed at anybody in particular... just thoughts catalysed by comments and attitudes visible through this thread.