How should financial institutions implement PSD2 SCA without creating excessive customer friction?

Start with risk based multifactor authentication for in scope payment and account information actions, then layer in dynamic linking so the approval is bound to the specific payee and amount. Separate the payment action from the authentication factor, protect confidentiality, and keep the journey accessible. The goal is stronger transaction assurance without making legitimate users abandon the flow.

Why PSD2 SCA Works Best When It Is Transaction-Specific

The friction problem is usually created by treating SCA as a generic login gate instead of a transaction assurance control. For payment flows, the value of SCA is highest when the customer can approve a specific action with minimal interruption, rather than repeatedly proving identity in ways that do not reduce payment fraud.

Dynamic linking is the key design choice because it binds the approval to the exact payee and amount, which reduces the value of a captured approval and helps distinguish a legitimate transaction from a modified one. That binding is also why the authentication step should be separated from the payment action, so the factor proves consent without exposing the customer to unnecessary re-entry or context switching.

For financial institutions, the practical target is not maximum challenge, but maximum assurance per unit of customer effort. Risk based multifactor authentication should therefore be used to step up checks only where the in-scope action, channel, device, or behavioural context justifies it, while keeping low-risk journeys fast enough that customers can complete them.

A useful design test is whether the customer still understands what they are authorising, and whether the approval remains valid if the transaction details change after authentication. If the flow does not make the payment details visible and stable at the point of consent, it may meet the letter of SCA while failing the trust goal that matters to the customer and the institution.

Where Friction Usually Appears in Payment Journeys

Excessive friction often comes from over-challenging routine actions, collapsing authentication and authorisation into the same screen, or using controls that are hard to use on mobile and assistive technologies. Each of those choices can push legitimate users out of the flow, even when the underlying security policy is sound.

The biggest implementation mistake is adding an extra step that does not materially reduce fraud risk. If the approval does not bind to the transaction, or if the institution still cannot distinguish a real customer action from a replay or substitution attempt, the extra friction is only cost, not control.

Design teams should also watch for channel inconsistency. A customer who sees one journey for card payments, another for account information actions, and another for recurring payments will experience the policy as arbitrary unless the differences are clearly tied to risk. Consistent logic, clear prompts, and predictable challenge behaviour reduce abandonment more effectively than simply shortening the flow.

Accessibility is part of security delivery here, not an optional polish item. If a required step is difficult to understand, cannot be completed reliably, or breaks on common devices, the institution will create avoidable exceptions, support calls, and fallback paths that often weaken assurance more than the original friction would have.

Risk and Threat Considerations

When SCA is implemented too loosely, attackers can exploit weak step-up triggers, transaction substitution, or poor binding between the approval and the actual payment. When it is implemented too aggressively, organisations create abandonment, call-centre workarounds, and usability exceptions that can become the real control weakness.

Failure mechanism: A generic second factor, or a challenge that is not cryptographically or procedurally tied to the payee and amount, can be replayed or repurposed for a different transaction. Overly burdensome journeys also encourage users and support staff to route around the intended control.

Impact: The institution loses either fraud resistance or customer conversion, and often both. The right balance is to make the control feel lighter for low-risk activity while making the approval stronger, clearer, and harder to abuse when the transaction genuinely warrants it.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

NIST CSF 2.0, CIS Controls v8 and NIST SP 800-63 set the technical controls, while PCI DSS v4.0 define the regulatory obligations.

Framework	Control / Reference	Relevance
NIST CSF 2.0	PR.AA — Identity Management, Authentication and Access Control	SCA is an authentication and access control decision for payment actions.
Recommendation — Apply PR.AA to enforce risk-based authentication and tightly scoped transaction approval.
CIS Controls v8	6 — Access Control Management	Payment approval should be limited to the exact authorised action with least privilege.
Recommendation — Implement Control 6 to restrict approval paths and reduce unnecessary authentication friction.
NIST SP 800-63	3 — Digital Identity Guidelines	Provides assurance concepts for authentication strength and step-up decisions.
Recommendation — Use SP 800-63 assurance concepts to calibrate when step-up authentication is warranted.
PCI DSS v4.0	8 — Identify Users and Authenticate Access	Payment environments need strong, usable authentication aligned to transaction risk.
Recommendation — Use Requirement 8 to authenticate access without adding avoidable payment-flow friction.

Practitioner Guidance

What to prioritise: Build the policy around transaction risk first, then tune the journey. In practice, that means measuring where step-up actually reduces loss, where it adds abandonment, and which payment types need the strongest binding of consent to transaction details.

What to verify: Confirm that the authentication step cannot be reused for a different payee or amount, that the customer can see the payment details at the point of approval, and that fallback paths do not bypass the intended assurance level. If any one of those fails, the flow is probably optimised for convenience rather than trustworthy payment confirmation.

Practitioner takeaway: The best PSD2 SCA design makes the approval more specific, not more annoying, so the institution should spend its complexity budget on binding and risk calibration rather than on extra prompts.