You may need to get a certificate to show that your property is fit for habitation. Certain properties don't need to get the certificate, but it is an offence to fail to apply for one if your property isn't exempt.
All rented properties must, at the very least, meet the basic fitness standard. However, even if your home meets the fitness standard it could still be regarded as unfit by inspectors from your local council. You should try to maintain the property to a standard that you would be happy to live in.