Just wondered how i adjust my shares now for tax after...

Just wondered how i adjust my shares now for tax after consolidation, i am using a Portfolio Manager and it only allows me to show what is bought and what is sold, and i haven't sold them,and if i adjust it to the new rate it screws everything up. What was the figure i would put in as the buying price.Have had these shares for some years.
Probably haven't explained this that well, but not had to do this before, so have been lucky.
Thanks good luck all