It's just happened to us, we owe them 3500!!! Every year, we told them exactly what we were earning, and told them everything they could possibly need. Last year, they decided we owed them money, and later told us we didn't. My wife spoke to them this time, they couldn't explain clearly where the error occured, but we obviously agreed to pay it back. We offered £50 per month, they wouldn't accept that, so they took £450 out of my salary today, and then £70 a month. Coz I can afford to lose £450 out of a months pay!! T*at*!!