Landlords are required by law to ensure:
That the electrical installation in a rented property is safe when tenants move in and maintained in a safe condition throughout its duration.
That a House in Multiple Occupation (HMO) has a periodic inspection carried out on the property every five years.
If your property is not an HMO, you are not legally obliged to do this. However, the ESC recommends that a periodic inspection and test is carried out by a registered electrician on your rental properties at least every five years.
Some useful tips provided by the Electrical Safety Council
Source: Electrical Safety Council