England and Wales
Tickets from a Council or Local Authority
Local Authority tickets will usually state they are issued under the "Traffic Management Act 2014". They also use the term "Penalty Charge Notice" and should not be ignored as these are Statutory fines. You can appeal in London to the Parking and Traffic Appeals Service or outside London, but within England and Wales, to the Traffic Penalty Tribunal.
The best source of help on these is the Pepipoo forum.
Tickets from a Private Parking Company
Tickets from Private Parking operators are known to mimic Local Authority ones but are essentially demands for spurious amounts of money for breaking fictitious rules. They use the term "Parking Charge Notice" as these are not penalties.
In some cases it is best to appeal especially if it the car is leased or hired or belongs to someone else. The "rules" are different for each company but essentially they will reject any appeal as these tickets are the only money they make. For help with these tickets use our parking ticket wizard.
Scotland and Northern Ireland
In Scotland and Northern Ireland there is no so-called "Keeper Liability" only the driver can be held to have agreed a contract - if such a contract exists. Unless there is a desperate need to contact the parking company e.g. lease or hire, then ignore but file all paperwork. There is more on this at Citizens Advice Scotland's web site.
Tickets at a Rail Station
All Rail Stations in the UK are covered by Railway Byelaws where a breach of these bylaws results in a statutory fine which can only be appealed at the Magistrates Court. Since it costs of Train Operating Companies (TOC) to take someone to court and any fines is paid to the Court and not the TOC, these companies have been ignoring the use of bylaws and using contract law instead.
There are a number of legal issues with this approach but the key one is that the Keeper cannot be be held liable for a parking charge issued on Rail land - though a number of parking contractors either falsely claim this or word their notices to imply this. More details on what to do will be available shortly but contact Passenger Focus (now called Transport Focus) or us for help.
Tickets at an Airport
As with Rail, most Airports are covered by Bylaws and the Keeper can never be liable. Some companies get round this by insisting whoever appeals was the driver irrespective of the facts of the event. So the advice is not to appeal or engage with these companies who clearly will say anything to extract money from the unwary.
Tickets from a Council / Local Authority
Pepipoo's motto is "Helping the motorist get justice". Started many years ago in response to provide information on Speeding tickets, the forum has grown to offer advice on Local Authority and private parking tickets. Go to the Pepipoo site for help for any Local Authority ticket.