[new299]

It is possible to know. In the UK it's easier to know than in other countries, private companies still have to disclose share ownership and file public accounts (which you can download from companies house).

It's just that this information is often not provided or explained. Why companies think it's ok to say "you'll get X shares" when X is a meaningless number without more information, is beyond me.

[arethuza]

There can be all manner of agreements in place that mean that the mapping from the share ownership structure pre-IPO/acquisition might not be straightforward.

e.g. When the company I co-founded went public there was a ratchet agreement in place (amusingly, which we'd tried to get removed at the time of the first round of VC investment) that gave us large amounts of new share options that was much larger than the employee share option scheme. Things like liquidation preferences also can also have a huge impact and as an employee your are probably not going to get visibility of all of these and I'm pretty sure none of this will be in Companies House!