You must register the death within certain timeframes:
England – within 5 days
Wales – within 5 days
Scotland – within 8 days
You can do this at the registry office closest to where the person passed away or at your local registry office.
The registry office will issue you with a death certificate – this is required by most organisations prior to settling any affairs.
The government's Tell Us Once service allows you to arrange the deceased's governmental affairs and covers a wide range of topics such as pensions and passports.