The catchphrase for TVL's current advertising campaign is that "it's all in the database".

The implication is that TVL have a list of addresses that are breaking the law, but this is incorrect:

In reality, the Royal Mail maintains a database of every postal address in the UK. This database is known as the Postcode Address File, and is available to anyone who wishes to purchase a copy (a corporate license currently costs around £80,000).

TVL purchase a copy of this database, and subtract the addresses of people who have purchased a television licence. This produces a list of addresses that do not have a television licence.

TVL then take the addresses on the list, and sort them by priority. Addresses in areas with a lower than average number of TV licences are targeted first, along with addresses that retailers are required to report whenever a television is sold.

Obviously this approach says nothing about the status of those addresses - the property may be empty, the owners may not own a television, the owners may own a television but not need a licence, the owners may have purchased a television for a different property, or the property may indeed be in need of a licence.

Unfortunately TVL take no account of this, and assume everyone is guilty until proven innocent. This is reflected in their letters, which become increasingly aggressive over time.