You can find out by using Shelter's tools here.
Renting direct from a landlord
Your landlord is legally responsible for protecting your deposit. It’s important to check that they have or you could struggle to get your money back without going to court. They should provide you with the documentation stating which scheme they are using along with your contract.
The three government-approved schemes are:
If your landlord is using any other scheme your deposit is not protected.
Renting from the University or living with the owner of the property
If you live in University accommodation or rent a room in a house with the owner, they do not legally have to protect your deposit.