There are two Accredited Trade Associations, these are The International Parking Community (IPC) [www.theipc.info] and the British Parking Association (BPA) [www.britishparking.co.uk]
There are two Independent Appeal Bodies, these are The Independent Appeals Service (IAS) [www.theias.org] and Parking On Private Land Appeals (POPLA) [www.popla.co.uk]. Your Parking Charge Notice or Notice to Keeper/Hirer will outline which Independent Appeals Service you can use.
The DVLA require all parking operators who wish to access their data to belong to an Accredited Trade Association (ATA). Parking Operators using the PaymyPCN Platform are members of ATA of part of their various compliance processes we are routinely audited by both the ATA and the DVLA.