It’s the age old question which no one seems to know the answer to. If you search the topic, there’s only one article that gives some insight into this. But there isn’t really a concrete answer.
What I’ve been able to gather is that most referees get paid either a daily rate or a match rate; while very few of the top level officials get paid a salary. According to Bizfluent, new referees earn approximately $90 per match, which comes to around £70 per match. There aren’t many sources to confirm this but based on what I’ve looked into, I’d say between £50-75 a match is a reasonable estimate. This amount is likely lower for lesser known, more local events.
The top referees, such as Jan Verhaas, Brendan Moore and (former ref) Eirian Williams; it’s safe to say that they earn substantially more (likely with a salaried structure) and could support themselves on a full-time basis.
A lot of snooker players starting out work part time in order to supplement their income and support themselves as they try to make ends meet as a professional. Similarly, referees tend to work other jobs alongside snooker while they try to gain more experience refereeing. A common example: Olivier Marteel also works as a nurse in and around the busy snooker schedule.
Additionally, expenses are something that are factored into a referee’s earnings. Most likely, they are reimbursed or covered for a certain level of their expenses. As stated on the EASB website (the organisation responsible for training prospect referees in Europe), things such as mileage for travelling to venues as well as hotel expenses are accounted for.
Again, a lot of this is speculation so it could be way off of what is actually the case. And I’m sure there won’t be any referees rushing to make statements about their earnings any time soon (understandably, why would they). But until then, I guess it will remain a mystery.