The data in Smartform is sourced from the Press Association (PA) and this is therefore the PA Private Handicap (i.e. performance rating figure).
PA will licence their racing data to a whole load of outlets, including many newspapers. They also directly publish the weekend paper Racing Plus, so the Smartform private handicap should tally with the ratings published in form guides there - although I've never checked.
I don't know how it's calculated and I doubt PA would reveal the full workings but like most private handicaps it has a basic read-across to the official handicapping scale (1pt = 1lb in weight, approx rating ceilings 140 on the flat, 180 over jumps).
