Damage deposit is not income, how do I record it

I run a holiday letting company and receive rental income as well as a returnable damage deposit, sometimes in the same payment. I have worked out how to split the two amounts on the invoice but need a way of categorising the damage deposit. If I mark it as miscellaneous income, it is recorded as income, which it isn't, I have to give it back unless there is damage. Occasionally I do keep money for repairs (twice so far)
How do I record all this?