osho
Turnover in excess of £ 32,800 must be declared, regardless of any gain or loss.
Tax free allowance is £ 8,200 in the 04-05 tax year.
The % rate you pay depends on your overall income. Capital gains are added to any earned income to determine which tax band you're in.
SB - believe it's totally tax free, but not 100% sure.
For options I use the Date of sale as the tax point. So when shorting options, I have to wait until either I close or expiry before I can fill in the return. That may be some months into the next tax year.