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In 2024, the Financial Conduct Authority (FCA) issued over £176 million in fines, much of it tied to inadequate anti-money laundering (AML) controls. Starling Bank alone faced a penalty of £29 million for weaknesses in its financial crime systems, while Metro Bank was fined £16.7 million for AML failures.
These cases highlight a growing reality: regulators now expect firms to prove not just who their clients are, but also where their money is coming from.
For many businesses, this means rethinking how Source of Funds Checks are performed. Manual processes like collecting PDFs, cross-checking payslips, or requesting employer letters are slow, error-prone, and increasingly seen as non-compliant.
That’s why compliance-focused platforms are adopting Source of Funds Check APIs.
By connecting directly to the client’s bank account using secure Open Banking infrastructure, these APIs provide real-time visibility into financial activity, no document uploads, and no guesswork. Whether you’re onboarding a property buyer, processing a contractor payout, or verifying deposits in legal workflows, API-powered checks offer clarity and control from the start.
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What Is a Source of Funds Check API? How It Works and When to Use It
What Is a Source of Funds Check?
A Source of Funds Check confirms the origin of money used in a specific transaction. In regulated industries like law, accounting, and property, this is often required to comply with anti-money laundering (AML) obligations.
Traditionally, these checks involve chasing down supporting documents:
- Bank statements
- Pay slips
- Employer confirmation letters
- Gift declarations
But these methods are slow, hard to verify, and vulnerable to manipulation.
That’s where Source of Funds APIs step in.
By connecting to a user’s bank account via Open Banking (with their consent), these APIs retrieve real-time data such as:
- Regular income sources (salary, benefits, pensions)
- One-time deposits (inheritance, sales proceeds, loan disbursements)
- Transaction timestamps and account ownership
- Matching the account holder’s name
Instead of waiting days for documents, you get verifiable insights in seconds, delivered through secure, audit-ready infrastructure.
Common Use Cases for Source of Funds Check APIs
| Industry | Use Case |
|---|---|
| Legal | Verifying funds for property purchases, settlements, or trust setups |
| Accounting | Checking income sources during client onboarding or AML reviews |
| Proptech | Screening buyers or tenants with verified bank transaction data |
| Fintech | Verifying deposits for account creation, payouts, or merchant approvals |
| Compliance | Supporting internal AML audits and audit trail generation |
📚 Guide to Open Banking Income & Balance verification
How Source of Funds, Proof of Funds, and Source of Wealth Differ
| Check Type | What It Verifies | Example Use Case |
|---|---|---|
| Source of Funds | Origin of money used for a specific transaction | £80K property deposit came from 12 months of salary |
| Proof of Funds | Whether sufficient funds exist in the account today | Client has £150K in a current account to cover purchase |
| Source of Wealth | How the client built their net worth over time | Net worth derived from 10+ years of business income |
Why APIs Are Better Than Manual Source of Funds Checks
Traditional verification methods rely on clients submitting:
- PDFs of bank statements
- Scanned pay slips
- Manually written explanations
These methods are slow, error-prone, and difficult to audit.
| Method | Speed | Accuracy | Compliance Readiness | Client Experience |
|---|---|---|---|---|
| Manual (PDFs) | 2–5 days | Variable | Often incomplete or delayed | Friction-heavy, outdated |
| API-Based (Finexer) | Under 1 hour | Verified at source | FCA-aligned and audit-ready | Seamless bank login process |
Top Benefits of Using a Source of Funds API
- Faster onboarding: Reduce verification time from days to minutes
- Stronger compliance: Receive tamper-proof, real-time data directly from banks
- Less friction: Offer a mobile-friendly, secure client experience
- Better decisions: Base approvals on validated financial activity, not guesswork
How It Works?
Finexer’s Source of Funds Check API is built on its Open Banking Data Aggregation framework. It allows your platform to securely access real-time financial data with full user consent, making verification faster, more accurate, and easier to audit.
1. Connect to the Client’s Bank
The user selects their bank and authenticates through a secure, consent-driven Open Banking journey. Finexer supports connections to 99 percent of UK banks.
2. Retrieve Financial Information
Once access is granted, the API collects key financial data, including:
- Regular income sources such as salary, pensions, or benefits
- One-off deposits, including loans, inheritance, or asset sales
- Complete transaction history and relevant account details
3. Confirm Identity
The system matches the account holder’s name from the bank with the user’s declared identity. This step verifies ownership of the account being checked.
4. Deliver a Structured Report
The API returns a clear, audit-ready Source of Funds report that includes:
- Verified income and deposit records
- Time-stamped transaction data
- Account holder verification
- Consent and access logs for compliance review
This process replaces manual document reviews with a secure, standardised verification method suitable for onboarding, compliance, and high-value financial workflows.
Integration Methods
1. REST API
Use Finexer’s Open Banking Data API directly through REST endpoints:
- Fully flexible integration into your backend
- Set verification parameters (e.g., salary range, deposit type)
- Webhook-based updates for real-time results
- Ideal for regulated platforms with custom onboarding flows
2. SDKs & Hosted Components
Fast-track integration using Finexer’s hosted bank login widgets and prebuilt flows:
- Embed components into your UI with minimal code
- Consent, account connection, and transaction retrieval are handled automatically
- Best for startups or mid-sized firms without dedicated backend teams
3. White-Label Flows
If you want a branded but maintenance-free experience:
- Finexer hosts the entire verification journey under your brand
- No need to register as an AISP or manage Open Banking flows internally
- Ideal for legal, accounting, and property platforms needing speed and compliance
Source of Funds Check API Pricing Models in the UK
1. Pay-As-You-Go (Transactional)
- You pay per completed Source of Funds check
- Ideal for platforms with fluctuating verification needs
- No fixed commitments or minimums
2. Subscription Plans
- Monthly fee for a set number of checks (e.g. 500–2000/month)
- Suitable for firms with predictable onboarding pipelines
- Sometimes bundled with other tools (e.g. ID checks, doc capture)
3. Hybrid Models
- Base monthly fee + lower per-check rates
- Balances predictability with flexibility as you grow
- Often includes tiered support or SLA options
4. Volume-Based Discounts
- Discounts are applied based on monthly verification volumes
- Finexer supports cost efficiency at scale without forcing long-term contracts
How Finexer Makes Source of Funds Checks Affordable
Finexer is designed to remove the cost and complexity from Source of Funds checks. It gives you access to real-time bank data, pricing that fits your usage, and everything you need to stay compliant, without expensive bundles or long deployment times.
✓ Built for Flexibility
Finexer doesn’t lock you into bundled AML platforms. You choose the specific APIs you need — whether it’s bank account access, income verification, or enriched financial history.
- Start with the Source of Funds and add features only if required
- Works for onboarding, compliance, or payment workflows
- Covers 99% of UK banks through a single API
✓ Affordable for Every Business Type
Finexer uses a usage-based pricing model with no setup fees, no hidden charges, and no long-term contracts.
- Transparent cost per check
- Volume-based discounts as you grow
- Works for both low-volume and high-frequency use cases
Whether you’re running a few verifications a week or thousands per month, Finexer keeps your costs in check.
✓ 2–3x Faster to Deploy
You don’t need to spend weeks building. Finexer provides:
- Developer-ready REST APIs
- Prebuilt, hosted bank login flows
- White-label options for a branded experience
Most businesses integrate and go live in under a week.
✓ Compliance Taken Care Of
Finexer is FCA-authorised and handles all compliance infrastructure on your behalf.
- No need for your own AISP registration
- Secure user consent flows and audit-ready reporting
- Aligned with UK Open Banking and GDPR standards
This saves you time, reduces legal risk, and lowers long-term operational costs.
✓ Start Small, Scale Smart
Finexer is built for businesses that want to move quickly without being locked in.
- Flexible APIs
- Fast onboarding
- Pricing that grows with you
Whether you’re an accounting platform, legal provider, or onboarding tech firm, Finexer helps you deliver compliant Source of Funds checks with less friction and lower spend.
Is Finexer authorised to perform Source of Funds checks?
Yes. Finexer is FCA-authorised as an Account Information Service Provider (AISP) and provides fully compliant access to Open Banking data for Source of Funds checks.
Do I need to be regulated to use Finexer?
No. Finexer handles the regulatory infrastructure, so you can use its APIs without registering as an AISP or building compliance systems yourself.
How long does a Source of Funds check take with Finexer?
Most verifications are completed in under a minute after the client logs into their bank account. Reports are generated instantly via secure API or webhook.
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