I've had a spare Oyster card lying around for a while, and decided that I would get my £5 back plus the PAYG credit on there. I tried at Stockwell twice (two different staff) and at Euston once to refund my Oyster card, and all three of them said that I needed drivers licence and a bank statement / utility bill. As I didn't bring a bank statement with me down to London to see a friend, I couldn't get it refunded. I tried one last time at Kings Cross St Pancras before my train back home and the guy did actually refund it, he just asked me to confirm some details and write down my current address.
I think I got lucky finding someone who would do it. I asked the lady at Stockwell if this was a recent thing, and she told me that it had been in place for a few years, but only recently have they been asked to enforce it by their bosses.
This got me thinking, what happens to the tourist visiting London for the weekend? I thought the idea was that you could refund them easily and at any time. There's going to be a lot of tourists out there stuck with an Oyster card they're never going to use again because they didn't bring a bank statement with them.
I should mention the Oyster Card I wanted to refund is registered, but they never even took it off me to check that it was or not, as soon as I mentioned I wanted a refund, I was always told if you don't have a bank statement or utility bill I can't refund it. No questions at all about whether it was registered or not.