It is assumed that a non-dependent adult living in your household will contribute towards your household costs, including rent and Council Tax. The benefits authorities will therefore deduct a sum of money from your Housing Benefit or Universal Credit and Council Tax Reduction award. This is called a non-dependant deduction.
Non-dependants are normally defined as anyone living with you aged 18 or over (21 if you are on Universal Credit) and for whom you do not receive Child Benefit. The amount deducted from your benefit is then generally based on the income the non-dependant receives. The deduction is applied regardless of whether or not they do actually give you any money for food, rent, electricity etc.
When making a claim for benefits to help with your rent or Council Tax bill, it is important that you properly define the status of any non-dependent adult living in your household. The non-dependant deduction rules can be confusing and the wrong deduction can sometimes be taken making a big difference to your Housing Benefit or Universal Credit and Council Tax Support award. If the non-dependent is in fact a lodger who pays you rent on a formal basis, then different rules apply