Clients who pay by card or Bacs Direct Debit can update their payment details at any time by visiting their client dashboard and clicking the "Update payment method" button.
The link was sent to you when you first signed up and entered your payment details. It is unique to you and will look something like thenumber.ninja/dashboard/7b5f2f285712ce8a14ae47e0a8ed3174d4053666.
Don't worry if you can't find it, email support@thenumberninja.co.uk and the team will be able to send it again.