I work in a co too small to report, but as I am Head of HR I did a report anyway (unpublished).
We had no issue but it's a very male dominated environment and the number of women is low so hard to really get a statistical feel. I don't really see any sexism in our workplace in terms of reward.
I was originally fixed term with a completion bonus, when they asked me to stay I said I would if they reflected the bonus in my salary - I'd been there a year and the co had a payrise in that time (but I didn't, which was fine) - I compare myself with the Financial Controller, male, same level of experience etc.
I was all geared up if line manager gave me a lower salary than him to ask why I wouldn't be getting the same - and actually, the sal he came back with was £3k more.
If there is a bonus, everyone gets it, the same (last year it was a week's pay, based on your own salary).
Our board is all male but it's only three people, two of whom re the company owners. It's very hard to recruit women in our key operational area, though we do try. When we do, they just get a salary based on their experience.
I agree that Self-ID is going to skew these results. Plus, using the word 'gender' now seems like an own goal!