It is estimated that 5,000 people in Wales who are paying a spare room subsidy could - and should - have been exempt.
Under the rule, anyone who has been in their home since before 1996 and has continually claimed housing benefit does not have to pay the subsidy.
A spokesperson for the Department of Work and Pensions say they are looking at the issue carefully and will take any necessary action.
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Farmer Gareth Wyn Jones is hoping for a festive online hit with footage of sheepdog Cap rounding up sheep.
It is expected to remain wet and windy for the rest of today, overnight and tomorrow. Conditions improving on Christmas Eve