I've advised him to email boss & say he's not been paid for x dates. He's on holiday last week/this week/next week and they don't seem to handle that well either ( used to casual staff/ no holiday pay)
They are a small business so no HR just a couple of casual/ part timers and the boss.
The pay tends to be late due to disorganisation rather than the money isn't there but they also aren't doing wonderfully at the moment so we don't want to hang on.