Hi Rory, You are only exempt from paying USC if Revenue tick the USC Exempt box in your tax credit certificate/P2C. If they don't, then you get charged USC on every single cent you earn, regardless of how much you get paid. If you are under the threshold, you must claim the USC you have paid during the year back at the end of the year. From what we've seen, Revenue mark very few people as USC exempt, so you'll need to claim the USC you've paid back from them. Regards, John.