# PSD2 and SCA

The European Union's Strong Customer Authentication (SCA) requirements became effective on September 14, 2019. These new requirements, part of the [second Payment Services Directive](https://ec.europa.eu/info/law/payment-services-psd-2-directive-eu-2015-2366_en) (PSD2) regulations, mandate that two-factor authentication be conducted on certain online transactions.

We outline the steps you must implement to build SCA-compliant purchases and account management workflows in [Building payment workflows](/commerce-api/payments/building-your-workflows.md).


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