Very successful independent musician Zoe Keating, who has had multiple run-ins with the unfair practices of collections societies giving money she's owed to major labels, just came across this same issue and wrote a blog post about her experience:
After a concert, there is this thing called “doing the settlement”. This is where the artist or their representative meets with the promoter, goes over the financial outcome of the night in relation to their contract…and gets paid. Sometimes the contract is for a percentage of the gross revenues, but more often for me, I get a guarantee and maybe a percentage of “net” if it was a positive number. The line item deductions that go into the calculation of net are things like sound & lights, staff, venue rental, advertising, insurance, etc. There tend to be many line items in the calculation of “net” and I can’t help but notice that ... read on."