To get your taxable income you take your gross pay & then subtract the personal allowance from it. Benefits in kind (company cars etc) are a different kettle of fish, if you have them, they're normally dealt with through a change to your tax code (which would mean a change to your personal allowance). The thresholds that ansteyg quoted are split up into either months or weeks (depending on how often you get paid) so you get a bit of your personal allowance each payday, an bit of your starting rate allowance each payday and so on.