Source of Funds vs Source of Wealth: An AML Guide for Accountants

Two phrases come up constantly in client due diligence and are often used as if they meant the same thing: source of funds and source of wealth. They are related, but they answer different questions, and the UK accountancy sector guidance asks for them in different situations. This guide explains the difference in plain language, then sets out when the 2026 guidance says an accountancy practice should check each one. For the wider process, see our guide to KYC and customer due diligence for accountancy practices.

Where this guide comes from

We used the CCAB's Anti-Money Laundering, Counter-Terrorist and Counter-Proliferation Financing Guidance for the Accountancy Sector, dated July 2026 and based on the law as of 1 July 2026. Paragraph 1.3.1 of the guidance states that it has been approved by HM Treasury. We also used ACCA's September 2026 summary of the changes. Paragraph numbers below are the guidance's own. This is general information, not legal advice.

The difference in plain language

The visible text of the guidance we read does not define either term, so the following is our own plain-language explanation, not a quotation. Source of funds is where the money for a particular transaction or engagement is coming from, for example a bank account, a sale or a loan. Source of wealth is how the client came to have their overall wealth, for example a business, an inheritance or a career. A client can have a perfectly respectable source of wealth and still send funds for one transaction from an unexpected place, which is why the two checks are kept separate.

When the guidance asks for source of funds

Paragraph 5.2.9 explains that under regulation 28(11)(a) of the Money Laundering Regulations 2017, businesses must scrutinise transactions during ongoing monitoring and, where necessary, the source of a client's funds. This is separate from the enhanced due diligence checks described below. Paragraph 5.2.10 says source of funds checks are needed when a transaction appears inconsistent with the firm's knowledge of the client, its business or its risk profile. The example it gives is a significant capital injection that the shareholders appear unable to fund.

ACCA's summary of the 2026 update makes the same point from the other direction: source of funds checks are relevant where a transaction seems inconsistent with what the firm knows about the customer, and firms need not check the source of funds for every transaction. In other words, this is a prompt-driven check, not a routine one.

When the guidance asks for source of wealth and funds together

The two checks travel together in enhanced due diligence. Paragraph 5.3.9 says that, for higher-risk clients connected to a high-risk third country, enhanced due diligence includes obtaining information on the source of wealth and source of funds of the client and its beneficial owners. Our guide to high-risk third countries and the FATF lists explains how those countries are identified.

For politically exposed persons, paragraph 5.3.26 says that, before entering into or continuing a relationship, firms must take adequate measures to establish the source of wealth and source of funds, alongside senior management approval and enhanced ongoing monitoring. Those measures "must be proportionate to the level of MLTPF risk identified", the guidance says, using its abbreviation for money laundering, terrorist and proliferation financing. In lower-risk PEP cases, paragraph 5.3.25 allows less intrusive steps. Paragraph 5.3.16 adds that refusing a business relationship solely because a client is a PEP is contrary to the FATF standards, and firms should refuse only where the risks cannot be managed. Our guide to politically exposed persons covers the wider picture.

Which enhanced due diligence cases are mandatory

Paragraph 5.3.7 lists the cases where enhanced due diligence applies. They include a high risk of money laundering, terrorist or proliferation financing; an occasional transaction involving a party in a high-risk third country; a business relationship with a client established in a high-risk third country; a PEP, or a PEP's family member or known close associate; false or stolen identification documents or information; any case where a transaction is unusually complex or unusually large, or follows an unusual pattern with no apparent economic or legal purpose; and any other case that by its nature presents a higher risk. Paragraph 5.3.8 adds that several risk factors together can trigger it.

How much evidence is enough

The guidance repeatedly uses the word proportionate. It does not set out a list of documents that must be collected for either check in the text we read, and paragraph 5.3.10 describes further steps, such as seeking additional independent sources to verify information, as optional enhanced measures. Whatever you do, document your reasoning, whether or not you decide enhanced measures are needed.

Practical steps (our suggestions)

• Write down, in your policy, the examples that would make you ask about source of funds, such as a capital injection that does not match the client's known resources.
• Record what you asked, what you received and why you were satisfied or not.
• For enhanced cases, separate the file note into source of wealth and source of funds so that neither is skipped.
• Match the depth of enquiry to the risk. A routine annual accounts client rarely needs the same evidence as a PEP.
• Train staff to recognise inconsistencies. Our CPD courses include financial crime topics.

What we could not confirm

The visible text of the guidance does not define source of funds or source of wealth, so our definitions are explanatory. We did not read the regulations themselves or the guidance chapters after section 5.4, and we have not covered what other supervisors, or other countries, expect. We also have not listed acceptable evidence, because the text we read does not. Check the full guidance and your supervisor's expectations before setting your own procedures.

Frequently asked questions

Do I have to check source of funds on every transaction?

No. ACCA's summary of the 2026 update says firms need not check it for every transaction, and the guidance links the check to transactions that look inconsistent with what you know.

Are source of funds and source of wealth the same?

No. In our explanation, one is about the money in a transaction and the other about how the client built their overall wealth.

Which clients need both?

The guidance names high-risk third country cases and PEPs among the enhanced due diligence situations where both are expected.

Can I refuse a client just because they are a PEP?

The guidance says refusing solely on that basis is contrary to the FATF standards.

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