Insider list
M&A / Merger ModelThe record an issuer and its advisers keep of everyone with access to inside information on a matter, including the date and time each person obtained it.
Also written: insider lists, list of insiders
An issuer, and anyone acting on its behalf such as its advisers, must maintain a list of every person with access to inside information on a given matter. It records who they are, the reason they have access, and the date and time at which they obtained it, and each person on it acknowledges in writing the duties and the sanctions that come with being on it.
It looks like administration and it functions as evidence. Where trading in a name is unusual ahead of an announcement, the regulator takes the issuer's and the advisers' lists, matches names and times against dealing records, and works outwards from there. The list is what makes an investigation tractable at all.
That is why the timestamps carry the weight. A list recording that somebody had access on a date rather than at a time is a much weaker document, and a list assembled after the event is worse than no list, because the gaps and the reconstruction are visible in it.
Being added to one is routine and is not an accusation. For a junior it is the mechanical reason a personal dealing request in that name is refused, and it is the reason a firm insists that accidental exposure is reported rather than assessed by the person who had it.
Worked example
An approach leaks and the target's shares move sharply two days before the announcement.
The regulator takes the insider lists, matches names and times against dealing records, and looks at accounts connected to anyone who had access before the move.
Somebody who came into possession by accident and reported it the same day appears on the list with a time against their name, which helps them. Somebody who did not appears nowhere, which does not.