Not sure if I'm putting this the right way but if somebody has two jobs and their employer wasn't aware of it could their PRSI and USC be calculated incorrectly due to the cut offs and tresholds??
Yes I think this happened to me last year. Didn't fully understand the details but I ended up paying back money cos the revenue had treated each job separately and therefore used too low a rate on one of them! It was bad news.
Wouldn't exactly be the revenue though. Your employer needs to have an idea of what your earn on a weekly basis. The case I'm thinking of involves a part time job plus casual hours with another employer
An employer isn't obliged to consider an employee's other income for USC purposes. The onus is on the employee to regularise the position in cases where a USC underpayment arises. Having said that, in a situation where an employee has (say) two employers, the employee can ask one of them to apply the marginal USC rate to their income from that source. That should eliminate the need for any further action.