DWP owe money, taken it straight of our debt - can they do this?

Hi, my husband never knew he could claim the carers element of UC until now. They said they owe us £1973.43 but have sent the entire amount to debt management to clear some of our debt. We were aware they could take 40% of our standard allowance but that was it. As I said to them if we received this correctly they would have been unable to deduct any but now taken it all. Can they do that?