I currently work for two employers, both of whom are aware that I do other work. Crucially, I'm not telling either one that I'm doing 40 hours (one is half-tim

I currently work for two employers, both of whom are aware that I do other work. Crucially, I'm not telling either one that I'm doing 40 hours (one is half-time, the other is somewhat less). Paying someone for "full-time" involves some amount of spare capacity, that you're paying for in order to have them available in case of emergency. But more fundamentally, you and your employer/customer should both be honest about what is being paid for/delivered.