i know it is down there, page-48

re: tax and other evils... sell vs which purchase You can choose to apply the proceeds of the sale against which ever allotment you choose. Depending on other CGT and personal income tax circumstances, you would normally want to apply this to the higher purchase allotment to reduce your capital gains tax payable at the end of the financial year. Another thing to consider is how long you have held your allotments for, as any shares you have held for more than 1 year you will only have to pay CGT on 50% of the profit, therefore it may be in your favor to apply your sale against your fist allotment.

Do the math and work out which one yields the lowest tax bill.

Hope this helps.