I'll link up Stripe's docs for SCA[1] as they have been very helpful for me in getting Leavetrack[2] set up for SCA.

PSD2 is the Second Payment Services Directive from the EU. A directive is required to be implemented in national law no more than two years after it is passed and whilst there have been delays, the past 12 months have seen a ramping up of banks implementing Strong Customer Authentication.

3DS (3D Secure) is like 2FA for debit/credit cards. In my case, I bank with Monzo and if a transaction requires 3DS, I have to open the Monzo app on my phone and confirm it. There are other aspects to SCA e.g. if I have used contactless payment frequently, I am more likely to be prompted to enter my PIN to confirm I still have my card.

[1] https://stripe.com/gb/payments/strong-customer-authenticatio... [2] https://leavetrackapp.com/