themos
Compliance·6 min read

PSD2 and SCA: What Merchants Need to Know in 2025

Strong Customer Authentication affects European payments. Here's the practical guide for merchants.

What is SCA?

Strong Customer Authentication (SCA) is a European regulatory requirement under PSD2. It requires two-factor authentication for most electronic payments in the EEA and UK.

The Two Factors

Authentication must use two of:

  • Knowledge: Something you know (PIN, password)
  • Possession: Something you have (phone, card)
  • Inherence: Something you are (biometrics)

When SCA Applies

  • Customer-initiated online payments
  • European cardholder paying European merchant
  • Above certain thresholds (varies)

Exemptions That Help

Low Value Transactions

Under €30 (with cumulative limits). Good for low-ticket items.

Trusted Beneficiaries

Customers can whitelist merchants. Useful for subscriptions.

Transaction Risk Analysis (TRA)

Low-risk transactions can skip SCA. Your PSP applies based on their fraud rates.

Recurring Payments

SCA required for first payment, exempted for subsequent fixed-amount recurring.

Impact on Conversion

SCA adds friction. Customers must complete 3DS2 authentication. Some will drop off. Optimization strategies:

  • Use exemptions where possible
  • Optimize 3DS2 flow for mobile
  • Work with PSPs that have good exemption engine
  • Monitor decline rates and adjust strategy

Technical Implementation

3DS2 is the primary SCA implementation method. Your PSP handles most of the complexity, but you need to:

  • Pass required data fields for risk assessment
  • Implement challenge flow in your checkout
  • Handle authentication failures gracefully

Key Takeaways

  • SCA is mandatory for most European card payments
  • Exemptions can reduce friction significantly
  • Work with PSPs that have good exemption engines
  • Monitor impact on conversion rates
  • Recurring billing has favorable treatment

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