What is it?
From April 2013, social housing tenants receiving housing benefit will have this payment reduced if they are deemed to have more bedrooms than they need.
Who will be affected?
Working-age council tenants, and working-age people renting from housing associations. Private tenants will not be affected. Families of military personnel, and foster carers will also be exempt.
How many bedrooms are you allowed?
One per adult, or one per couple. Children under 16 will be expected to share if they are the same gender, and children under 10 will have to share whatever their gender. Disabled tenants with full-time or overnight carers can claim a room for the carer. Other special circumstances will also be considered.
How much could you lose?
Housing benefit will be cut by 14% for the first extra bedroom, and by 25% for two.
Why is the government doing it?
To cut the housing benefit bill, free up space for overcrowded families, and encourage people to get jobs. But opponents say the changes will lead to more homelessness and greater rent arrears.