After the tenancy deposit has been paid it is a legal requirement that the deposit is registered in a government approved deposit scheme within 30 days. The deposit will be used in the case of repairing any damage above fair wear and tear that may happen during the tenancy, for none payment of rent or if the property requires professional cleaning. A detailed inventory done at the start of your tenancy combined with periodic inspection reports will help assess if any deductions are deemed fair or necessary.