As you say, "every ones tax liabilities and assets differ" and what is an advantage to one tax payer may be a disadvantage to another
If you make a loss in a particular year you can deduct those losses from other income eg salary. If you are an investor those losses are capital and can only be offset against capital gains
Expenses can be deducted eg if you use half you computer time for trading then you can depreciate half its cost; the software such as @Icarus (see note below) mentioned can be depreciated, a proportion of your internet costs can be claimed etc etc
There are other posts on record keeping and software but it seemed to be agreed that if you are going to buy sell particular parcels within one particular holding then Excel spreadsheet is probably the way to go. For simple FIFO, Ave Cost, or LIFO then an off-the-counter software program should suffice
