I overpaid NIC's during the tax year 2010/2011.
How do I know this? Well I was on maternity leave so only earned about £1000 more than the personal limit and at least 50% of this was taken off as NIC, which is too much.
Many people wouldn't notice this necessarily but I did and have been meaning to contact the tax office to sort out a refund.
I did today and had a very odd conversation with the (very nice) lady which went like this:
Me: I've overpaid NIC's and want a refund
Her: How do you know you've overpaid.
Me: