What is Strong Customer Authentication: A Complete Guide

If you’re an Indian business looking to expand into the European market,or already serving EEA customers,understanding Strong Customer Authentication (SCA) is essential for seamless payments and compliance. Strong Customer Authentication (SCA) is a regulatory requirement under the Payment Services Directive 2 (PSD2) in Europe, aimed at reducing online fraud and making digital payments more secure. In simple terms, SCA ensures that customers are who they say they are,by asking for more than just a password or card number during transactions.

What Does Strong Customer Authentication Mean?

Strong Customer Authentication (SCA) is a security requirement that ensures customers prove their identity using at least two independent authentication factors before completing electronic payments. This multi-layered approach significantly reduces fraud risk by making it much harder for unauthorised users to complete transactions.

If you’re an Indian business looking to expand into the European market,or already serving EEA customers,understanding Strong Customer Authentication (SCA) is essential for seamless payments and compliance. Strong Customer Authentication (SCA) is a regulatory requirement under the Payment Services Directive 2 (PSD2) in Europe, aimed at reducing online fraud and making digital payments more secure. In simple terms, SCA ensures that customers are who they say they are,by asking for more than just a password or card number during transactions.

Think of it as an extra layer of protection, especially for electronic payments, whether they’re made online or in-store. The goal? To make sure the person initiating a payment is the actual account holder.

To comply with SCA, a payment must include at least two of the following three authentication factors:

• Knowledge: Something only the user knows (e.g., a password or PIN)
• Possession: Something only the user has (e.g., a mobile device or hardware token)
• Inherence: Something the user is (e.g., fingerprint or facial recognition)

Comparison of Authentication Methods

Authentication Method	Security Level	User Experience	SCA Compliance
Password + SMS OTP	High	Moderate friction	Compliant
Biometric (fingerprint/face)	Very High	Seamless	Compliant
Push notification + PIN	High	Low friction	Compliant
Password only	Low	Seamless	Not compliant

This requirement is mandatory for most electronic payments in the European Economic Area (EEA) and is enforced by banks and payment providers.

Example: When a customer in the EU tries to make an online card payment, they might receive a one-time password (OTP) on their phone (possession), enter a PIN they know (knowledge), or verify using their fingerprint (inherence). This layered security approach makes it harder for fraudsters to bypass authentication,even if they get hold of card details.

Strong Customer Authentication Example

Let’s look at how SCA works in a real-world scenario:

Scenario: You’re an Indian exporter selling handcrafted goods to customers in Germany through your e-commerce website. A customer in Berlin wants to purchase a ₹15,000 order using their debit card.

Here’s what happens:

1. Customer initiates payment: They enter their card details on your checkout page and click “Pay Now”
2. SCA triggers: Because both the merchant (you) and the customer’s bank are within the EEA scope, SCA is required
3. First factor,Knowledge: The customer is redirected to their bank’s authentication page, where they enter their online banking password
4. Second factor,Possession: The bank sends a one-time passcode (OTP) to the customer’s registered mobile phone
5. Customer completes authentication: They enter the OTP within the time limit
6. Payment approved: Once both factors are verified, the payment is authorised and you receive confirmation

Key Changes and Impact on Businesses of SCA

SCA has fundamentally changed how businesses process payments in the EEA. The main impacts include:

• Enhanced Authentication Requirements: All customer-initiated electronic payments now require multi-factor authentication
• Operational Changes: Businesses must integrate SCA-compliant payment flows and handle authentication failures
• Compliance Obligations: Non-compliance can result in payment declines and potential regulatory penalties
• Customer Experience Impact: Additional authentication steps may increase checkout friction but significantly reduce fraud

For Indian businesses, this means ensuring your payment infrastructure can handle SCA requirements when serving European customers, or risk losing sales due to declined transactions.

When Do You Need Strong Customer Authentication?

Strong Customer Authentication (SCA) applies to customer-initiated electronic payments within the European Economic Area (EEA). This includes both online transactions (like purchasing on an e-commerce site) and offline contactless payments (such as tapping a card at a POS terminal).

Here are the most common scenarios where SCA is required:

• Online card payments made by customers in the EEA
• Adding a new beneficiary or initiating a bank transfer via online banking
• Contactless in-store payments after certain limits are crossed (e.g., cumulative amount or number of transactions)

However, SCA is not required in all cases. There are several important exemptions and edge cases:

• Merchant-initiated transactions (MITs): These are payments made without the customer actively involved,like subscriptions or recurring billing after the initial authentication.
• Low-value transactions: Payments below €30 may be exempt unless a threshold is exceeded.
• Trusted beneficiaries: If a customer has whitelisted a merchant, future payments to that merchant might bypass SCA.
• Corporate payments made using secure, dedicated payment processes.
• Transactions where either the cardholder or merchant is outside the EEA: SCA typically doesn’t apply to these cross-border scenarios.

Note for Indian Businesses: If you’re serving customers in the EEA, Razorpay ensures your payments are processed without compliance hiccups. Our platform automatically supports SCA-compliant flows, so your transactions go through smoothly,every time.

How Strong Customer Authentication Works in Practice

Strong Customer Authentication works by requiring customers to verify their identity using two or more authentication factors during payment. For online payments, this typically involves 3D Secure 2 protocols, while offline payments use chip-and-PIN or biometric verification methods.

Authenticating a card payment under SCA depends on whether the transaction happens online or in person.

SCA Requirements (The 2-out-of-3 Rule)

To meet SCA compliance, you must authenticate your customers using at least two factors from three distinct categories. This is known as the “2-out-of-3 rule”-and it’s crucial that these factors remain independent of each other.

Here’s what that means in practice:

Independent Factors: If one authentication method is compromised, it shouldn’t affect the others. For example, if a fraudster steals your password (knowledge), they still can’t access your account without your phone (possession) or fingerprint (inherence).

Minimum Two Factors: You can’t use two factors from the same category. For instance, using both a password and a security question wouldn’t qualify, as both are “knowledge” factors. You need factors from different categories,such as a password (knowledge) plus a fingerprint scan (inherence).

This multi-layered approach is what makes SCA significantly more secure than traditional password-only authentication. Even if fraudsters obtain one piece of information, they’re still blocked from completing fraudulent transactions without the second factor.

For Online Payments:

The most common method is 3D Secure, specifically 3D Secure 2 (3DS2),an updated protocol that supports SCA and offers a better user experience. Here’s how it works:

1. Customer initiates payment on an e-commerce site.
2. They are prompted to authenticate via:
   • OTP sent to a registered device (knowledge + possession)
   • Fingerprint or face scan if using Apple Pay or Google Pay (inherence)
   • Push notification from their banking app
3. Once authentication is successful, the payment is completed.

Many modern payment providers,like Stripe, Razorpay, or Adyen,have built-in authentication flows to make this process smooth. For example, they allow biometric verification through platforms like Apple Pay, which satisfies SCA without adding friction.

Why Choose Razorpay for SCA Compliance? Seamless SCA flows tailored for Indian exporters and merchants Real-time updates to keep you ahead of compliance changes Dedicated support for cross-border transactions Simple, secure integration for Indian businesses of all sizes Learn how Razorpay helps Indian businesses expand globally

For Offline Payments:

For in-person card payments, authentication typically involves:

• Inserting the card and entering a PIN (knowledge + possession)
• Contactless transactions, which may skip SCA for small amounts but trigger authentication after set thresholds.

Fraud Liability, PSD2, and Secure Authentication Protocols

When transactions are SCA-compliant, fraud liability shifts from merchants to the cardholder’s bank, providing significant protection for businesses. Secure authentication protocols like 3D Secure 2 not only ensure compliance but also reduce chargeback risks.

SCA doesn’t just enhance payment security,it also shifts the liability for certain types of fraud.

When a transaction is SCA-compliant, the responsibility for unauthorised payment disputes lies with the cardholder’s bank, not the merchant. This reduces your risk as a business owner, especially for online transactions.

Why 3D Secure Matters:

• 3D Secure 2 is the go-to solution for meeting SCA requirements in online card payments.
• It helps authenticate the cardholder, reducing fraud and boosting trust.
• It also protects merchants by transferring liability to the issuer bank if the transaction meets SCA standards.

So, beyond compliance, using 3DS2 helps lower chargeback risks and improve fraud protection,critical for high-volume online businesses.

Exemptions to Strong Customer Authentication Rules

Not all transactions require Strong Customer Authentication. The regulation allows specific exemptions based on risk level, transaction amount, or type of payment. These exemptions help maintain a smooth customer experience without compromising security.

Real-Time Risk Analysis and Transaction Monitoring

Real-time risk analysis (Transaction Risk Analysis or TRA) is a sophisticated system that evaluates the fraud risk of each transaction in real-time. Payment providers use machine learning algorithms and historical data to assess factors like:

• Customer behavior patterns
• Device fingerprinting
• Transaction amount and frequency
• Merchant risk profile

Based on this analysis, low-risk transactions may be exempted from SCA, while high-risk transactions require full authentication. The effectiveness of TRA depends on the payment provider’s fraud rate,lower fraud rates allow for higher exemption thresholds.

That said, banks and card issuers ultimately decide whether to accept an exemption. As a merchant, you can request an exemption, but you’ll need to support full authentication if it’s denied.

Let’s break down the most common SCA exemptions:

1. Transactions with Low Risk

If a transaction has a low risk of fraud, and the payment provider or bank has robust fraud monitoring systems, SCA can be skipped. This is known as Transaction Risk Analysis (TRA).

For transactions up to €100, payment providers must maintain a fraud rate of 0.13 percent or lower to utilise the TRA exemption, while for transactions up to €250 the threshold tightens to 0.06 percent, and for transactions up to €500 the threshold requires maintaining a fraud rate of 0.01 percent or lower.

2. Small Payments Under €30/£25

Payments below €30 or £25 may not require SCA.
However, SCA will be triggered if:

• More than five consecutive low-value transactions are made without authentication, or
• The total value of exempted transactions exceeds €100.

3. Regular Recurring Payments

Fixed-amount subscriptions (like Netflix or Spotify) are typically exempt after the first transaction, which requires SCA.
Subsequent payments of the same amount and recipient can skip authentication.

4. Merchant-Initiated Payments (e.g., Variable Subscriptions)

These are payments initiated by the merchant, not the customer, like metered billing or top-ups.
They’re exempt as long as the initial setup involved SCA and the customer agreed to it.

5. Phone Orders and Mail Orders (MOTO Payments)

MOTO payments are not subject to SCA because they aren’t considered electronic transactions initiated by the customer.
These should be flagged properly in the payment request to avoid declines.

6. Business or Corporate Payments

Payments made through secure corporate payment systems (like lodge cards or virtual cards used by travel agents) may be exempt.

7. Payments to Trusted Merchants

Customers can whitelist a merchant with their bank. Once a business is marked as “trusted”, future payments may not require SCA.
Note: Only the bank can manage this list, not the merchant.

What Happens If an Exemption Is Rejected?

If an SCA exemption is rejected by the bank, the customer must complete full authentication to proceed with the payment. Your business should implement fallback flows that seamlessly guide customers through the authentication process without causing transaction abandonment.

Even if a transaction qualifies for an exemption, the bank or issuer has the final say. If they decline the exemption, SCA is required to complete the payment.

What should businesses do?

• Implement fallback flows: Make sure your checkout experience can seamlessly handle both exempted and authenticated transactions.
• Communicate clearly: If extra steps are required, inform customers why, so they don’t drop off.
• Use modern payment providers: Platforms like Razorpay or Stripe automatically handle exemptions and re-route users to authentication if needed,minimising friction.

Potential Challenges and Issues with Strong Customer Authentication

While SCA significantly enhances payment security, it can introduce several challenges for businesses and customers:

Common Challenges:

Common challenges include:

• Increased Cart Abandonment: Additional authentication steps can cause customers to abandon purchases
• False Declines: Research shows 99 percent of merchants experienced increased payment declines following SCA implementation, with the average merchant seeing a 37 percent increase in declined transactions
• Technical Complexity: Implementing multiple authentication methods and fallback flows requires significant development resources
• Customer Education: Users may not understand why additional steps are required, leading to confusion and support requests
• Mobile Experience Issues: Authentication flows can be particularly challenging on mobile devices

Successful SCA implementation requires careful planning, robust testing, and ongoing optimization to minimize these challenges while maintaining compliance.

Mitigation Strategies:

• Implement seamless authentication methods like biometrics where possible
• Provide clear communication about security benefits
• Use intelligent exemption strategies to reduce unnecessary friction
• Partner with payment providers that offer optimized SCA flows

Conclusion

Strong Customer Authentication is a critical layer of security that protects both businesses and customers from online payment fraud. While compliance is mandatory in the EEA, the right use of exemptions can strike a balance between security and seamless checkout.

Razorpay helps Indian businesses stay ahead of compliance requirements while ensuring smooth payment experiences for their global customers. By working with Razorpay, which supports smart authentication flows, businesses can stay compliant without compromising on user experience.

Frequently Asked Questions (FAQs)

1. What is strong authentication?

Strong authentication is a security process that requires users to provide two or more verification factors from different categories (knowledge, possession, inherence) to prove their identity. It’s designed to be significantly more secure than single-factor authentication methods like passwords alone.

2. What is the difference between strong customer authentication and 3D Secure?

Strong Customer Authentication (SCA) is the regulatory requirement under PSD2, while 3D Secure is one of the technical protocols used to implement SCA for online card payments. 3D Secure 2.0 is specifically designed to meet SCA requirements and provides a better user experience than the original 3D Secure protocol.

3. What are examples of strong authentication methods?

Common examples include SMS OTP + password, fingerprint + PIN, facial recognition + device possession, push notifications + biometrics, and hardware tokens + passwords. Each method combines at least two different authentication factors.

4. How does Strong Customer Authentication impact online payments?

SCA adds an extra layer of security, requiring customers to verify themselves with two or more factors during checkout. This reduces fraud but can add friction if not implemented well.

5. What are the elements of Strong Customer Authentication?

SCA requires at least two out of three of the following:
Knowledge (something the customer knows – e.g., password or PIN)
Possession (something the customer has – e.g., phone or card)
Inherence (something the customer is – e.g., fingerprint or facial recognition)

6. How do I set up Strong Customer Authentication on my website?

Use a payment gateway that supports SCA (like Razorpay or Stripe). Ensure your checkout flow supports 3D Secure 2, fallback options, and exemption handling.

7. Who needs to comply with SCA regulations?

Any business processing electronic payments initiated by customers within the EEA must comply with SCA. This includes e-commerce sites, apps, and service providers.

8. Does SCA apply to all online transactions?

No. Exemptions apply for low-risk transactions, small amounts, recurring payments, and more. However, banks can still require authentication, even if an exemption is requested.

9. What happens if an SCA exemption fails?

The customer will be prompted to complete authentication using methods like OTP or biometrics. If they fail to authenticate, the payment may be declined.