I'm really sorry to hear about this, this government are vile.

I've been thinking though, where it could have gone wrong according to these rules (Which do as already said clearly state bonus and overtime can be included). I think perhaps here's the problem......

Total salary, including bonus, overtime can be included if the sponsor has been working for that employer for a year. He would have earned that in a year, and this would be his income.
He submitted for 7 months, not 12.

MAYBE if he's worked for that employer over a year, if he dug out his earlier 5 wageslips, then this would have been ok. Unfortunately, they are now also saying I think that appeal can't be made with extra information which should have been submitted at the initial time of application.

Alternatively he could have submitted just 7 months, if he had a number of jobs, and those employers would have written in letters stating that his eventual combined income would be over £18,600 - the base income. Similarly, he would only have needed to submit 6 months wageslips, if his current employer could have written the letter saying his base is £18,600 or over.

I guess their reasoning is that overtime can't be guaranteed for future and they won't count it, but they will count if it was past paid with proof and this took the income over.

Again, really sorry to hear this.