well, when someone accumulates shares in a company then until...

well, when someone accumulates shares in a company then until they reach 5%, they don't need to be "identified" as a Substantial holder...once they hit that mark, any major change in their holding needs to be announced via an announcement - all the way from 5% to 19.9%... if they hit 19.9% then they have to announce their "intentions" (are they about to go for a complete TO or something like that)... now they can accumulate only 3% (need to verify this) every year and not any more without showing their hand...

there is an ASX explanation for this, so please check that out, I could be out of whack in terms of % above 20%... hope this helps