Source of Wealth API: Complete Guide for UK Firms

Financial institutions in the UK are under growing pressure to explain not just how much money a client has, but where it comes from. According to the Financial Conduct Authority (FCA), firms across banking, property, and wealth management continue to face rising scrutiny over Source of Funds (SOF) and Source of Wealth (SOW) checks. Compliance costs have risen by over 60% in the past three years, and nearly half of all regulated firms admit they still rely on manual verification methods.

At the same time, the UK’s financial landscape is becoming increasingly complex. The median household wealth now stands at £293,700, while the top 10% of households hold more than £1.2 million in assets (ONS, 2024). For accountants, lawyers, and fintech platforms serving these clients, manual wealth verification isn’t scalable, especially when each client’s financial history can stretch across decades and multiple asset classes.

To address this gap, firms are now adopting Source of Wealth APIs. These APIs use Open Banking and regulated data feeds to automatically verify income streams, large deposits, and asset origins within seconds. Instead of chasing PDFs and self-declared statements, compliance teams can access a structured, auditable “story of wealth” backed by real transaction data. This shift marks a new phase of digital due diligence in the UK — faster, data-driven, and regulator-ready.

What Is a Source of Wealth API?

A Source of Wealth API is a regulatory technology tool that helps businesses identify how a client accumulated their overall wealth over time. Unlike a Source of Funds check, which focuses on the specific money used for a transaction, Source of Wealth verification looks at the broader picture — salary, business income, asset sales, inheritance, or investments.

Through regulated data connections such as Open Banking, a Source of Wealth API securely retrieves a customer’s financial data directly from their bank accounts. It then analyses patterns like recurring income, one-off deposits, and account ownership to build an auditable explanation of where the wealth originated. This replaces slow, manual document reviews with real-time data intelligence that’s already compliant with the UK’s Money Laundering Regulations (MLR 2017).

For example, when a law firm or financial adviser needs to verify that a client’s funds for a £500,000 property purchase came from legitimate savings or business proceeds, the API can instantly trace and categorise historical transactions to support that conclusion. This gives firms clear, evidence-based insight while maintaining full consent and data protection standards.

Why UK Firms Need a Source of Wealth API

For UK-regulated firms, verifying a client’s wealth is no longer just a compliance formality. The Financial Conduct Authority (FCA) and HMRC expect detailed Source of Wealth (SOW) evidence for higher-risk clients, politically exposed persons (PEPs), and large transactions. Yet, according to industry surveys, over 70% of UK compliance teams still rely on manual statement reviews or self-declared financial histories — processes that are slow, error-prone, and often insufficient during audits.

A Source of Wealth API eliminates these inefficiencies by automatically gathering structured, consented financial data directly from bank accounts. It can verify recurring income streams, detect one-off deposits such as asset sales or inheritance, and identify inconsistencies that could signal risk. This not only strengthens AML due-diligence but also reduces onboarding time from days to minutes.

For accountants, solicitors, and fintech platforms, the impact goes beyond compliance. Automated wealth verification helps teams handle higher client volumes without adding administrative overhead. It also provides a transparent audit trail, a crucial advantage when regulators or auditors request proof of how client wealth was assessed. In short, a Source of Wealth API transforms what used to be a manual compliance burden into a reliable, scalable workflow built for modern UK regulations.

Key Features to Look for in a Source of Wealth API

Selecting the right Source of Wealth API depends on how deeply your organisation needs to verify financial origins and integrate those checks into your workflow. Below are the most important features UK firms should prioritise:

1. UK Bank Coverage

Choose an API with direct connectivity to 99% of UK banks through Open Banking. Broader coverage ensures that your clients can connect accounts from major retail, business, or savings banks without delays or exclusions.

2. Historical Transaction Access

A strong Source of Wealth API should provide 12–24 months of transaction history, allowing compliance teams to build a detailed view of how wealth was accumulated over time from recurring income to asset liquidations.

3. Identity and Account Matching

The API should automatically verify that the connected bank accounts belong to the declared client. This prevents mismatches or third-party connections that could indicate hidden funds.

4. Categorisation and Data Enrichment

Modern APIs go beyond raw transactions. They use enrichment engines to classify income, spending, and deposits — turning unstructured data into an understandable financial narrative that’s ready for audit.

5. Consent and Audit Logs

Every data access should be traceable, with timestamped consent records and secure audit trails that align with GDPR and FCA requirements.

6. Developer-Friendly Integration

Look for RESTful endpoints, sandbox testing environments, and clear documentation. This helps your technical team integrate the API quickly without heavy infrastructure costs.

7. Flexible Pricing and Scalability

For firms handling variable client volumes, usage-based or tiered pricing ensures affordability while maintaining enterprise-grade performance.

8. FCA Authorisation

Finally, ensure the provider operates under the UK’s regulatory framework as an Authorised Account Information Service Provider (AISP). This guarantees legal compliance, data security, and credibility during client due diligence.

How Source of Wealth APIs Improve Compliance and Efficiency

Traditional Source of Wealth checks often depend on manual document collection — clients uploading bank statements, payslips, or asset-sale contracts. These methods are slow and leave room for human error or incomplete data. A Source of Wealth API automates the process by securely accessing and analysing financial data directly from the client’s accounts, giving compliance teams instant clarity and reducing onboarding times by up to 80%.

From a compliance perspective, automation ensures consistent, repeatable verification aligned with the UK Money Laundering Regulations (MLR 2017). Every action, from client consent to data retrieval, is recorded in an auditable trail, helping firms demonstrate due diligence during FCA or HMRC reviews. With the growing number of AML enforcement actions in the UK — more than £400 million in fines issued between 2021 and 2024 — maintaining complete data trails has become essential.

Operationally, APIs reduce manual workloads and eliminate back-and-forth communication with clients. Instead of chasing missing statements, teams can instantly confirm income sources, asset liquidity, or inheritance inflows. For firms handling hundreds of cases per month, this translates into substantial time and cost savings while strengthening regulatory confidence.

Finexer: The Leading Source of Wealth API Provider in the UK

FCA-Regulated and UK-Focused

Finexer sits at the forefront of the UK’s Open Banking ecosystem, offering a fully compliant and automated approach to Source of Wealth verification. As an FCA-authorised Account Information Service Provider (AISP), Finexer provides regulated firms with real-time, consent-based access to financial data from 99% of UK banks. This foundation ensures that every data request is secure, traceable, and compliant with the Money Laundering Regulations (MLR 2017) essential for firms managing client onboarding and enhanced due diligence.

Real-Time Wealth Verification

Finexer’s Source of Wealth API enables instant verification of how clients built their wealth — eliminating manual statements and unverified declarations. The API analyses verified banking data to detect recurring income patterns, asset-sale proceeds, dividends, or inheritance deposits, transforming them into an audit-ready financial profile. This helps regulated sectors such as law, property, accounting, and wealth management accelerate client onboarding while maintaining full compliance for FCA or HMRC reviews.

Designed for Fast, Flexible Implementation

Finexer’s implementation model combines usage-based pricing, white-label capability, and hands-on onboarding support lasting 3–5 weeks. This approach allows firms to deploy solutions up to 2–3x faster than the market average while keeping their own branding and client experience intact. Supported by clear documentation and responsive developer assistance, Finexer gives teams a reliable, developer-first way to automate compliance without unnecessary complexity.

Trusted by UK Businesses

With its regulated infrastructure, real-time data intelligence, and transparent design, Finexer has become a trusted choice for UK businesses aiming to automate Source of Wealth and Source of Funds checks. The platform turns regulatory verification into a streamlined process, ensuring accuracy, auditability, and speed across every client journey.