We will let you know exactly what you need to provide as your application progresses, and a lot of the information is collected in our dashboard.
You can start the process here.
But to prepare, you should have the following ready to start:
Full names of all applicants, including income and deposit boosters
Income figures and types for all applicants (including pension and self-employed income)
UK residency or visa status of all applicants excluding deposit boosters
Know how much deposit you will provide and how much any other people are providing to help you
Your credit score rating (usually ranges from poor to very good)
The email address you will use for your application (more can be added once the mortgage in principle is created)
Make sure each applicant has three years of UK address history excluding deposit boosters
Information about any criminal convictions for all applicants