It is important that your oil tank is visually checked regularly and serviced annually. Your heating engineer should complete an inspection of your oil tank as part of your annual boiler service. If the engineer discovers any issues, such as a leaking tank or water ingress then it is likely they will make recommendations to how these can be rectified. Whilst it is not law to fix these issues, you are responsible for the environmental impact these issues could cause. It’s worth checking your home insurance for damage to oil tanks as many do not include this as standard.