A key aim of the new regulation is to help prevent fraud and market abuse so firms are required to hold and report more information about its customers.
The main change surrounds details of your nationality/nationalities and providing something called a National Client Identifier (NCI). In the case of UK nationals the NCI is your National Insurance number. Non-UK nationals, and anyone who has multiple nationalities, may be asked for a different NCI, e.g. your passport number.
Additionally, if you have a third party linked to your account who makes investment decisions on your behalf, then this information will also be requested from the third party. If that third party is a company, different information will be required.
It is vital that you provide this information as failure to do so may mean you cannot trade after 2 January 2018. This includes standing instructions such as Regular Investments or Dividend Reinvestments.