YYour UK or international (in specific countries) mobile number. We'll use your mobile number to text you an activation code. You can see a full list of the available countries here.
YYour personal details - this includes your full name, date of birth, and post code. This helps us identify you as a customer, and allows you to register.
YYour NatWest account number and sort code - this again helps us to identify you further.
YYour 16-digit debit card number. Entering your debit card number can help you get access to Online Banking faster, but not having it won't stop you registering for the app.