KYC, KYB and KYS explained for UK marketplaces: what each check covers, which sellers need which, the UK rules involved and a simple seller checklist.
KYC (know your customer) checks a person. KYB (know your business) checks a company and the people behind it. KYS (know your seller) is how a marketplace combines the two for the people and businesses that sell on it: KYC for individual sellers, KYB plus KYC on the key people for company sellers, then ongoing screening for both. Most UK marketplaces need all three working together, with the depth of checks set by risk: what is being sold, how much, and how money moves.
KYC means verifying that an individual is who they claim to be. For a marketplace seller that usually means:
The output is a decision (approve, decline or refer for review) plus the evidence behind it.
KYB verifies a business. For a UK limited company seller, that means checking:
KYB always includes some KYC: you verify the business, then verify the person acting for it and the people who control it.
KYS (know your seller) is not a separate legal standard; it is a practical term for the seller-onboarding programme a marketplace runs. It answers three questions:
KYS also covers marketplace-specific signals that a bank's KYC would not: duplicate or linked accounts, mismatches between the seller's details and payout details, and rules for higher-risk categories.
KYA (know your agent) is a newer term for checking software agents, such as AI assistants, that act or buy on behalf of a person or business. The idea is to confirm which person or company stands behind an agent and what it is allowed to do. It is still an emerging practice with no settled UK standard. TrustVerify does not offer KYA checks; for marketplaces, the priority remains verifying the people and businesses that sell. When choosing a provider for that, see our guide to choosing KYC software.
| KYC | KYB | KYS | |
|---|---|---|---|
| Who is checked | An individual | A business and its controllers | Every seller on a marketplace |
| Core checks | ID document, liveness, face match, address, screening | Companies House, officers, PSC/UBO, screening | KYC or KYB by seller type, plus marketplace rules and monitoring |
| When | Onboarding, then re-screening | Onboarding, then monitoring changes | Onboarding, before payouts, and ongoing |
| Main purpose | Prove identity | Prove the business is real and who controls it | Keep fraudulent or prohibited sellers off the platform |
A risk-based approach usually works better than one fixed flow. A typical starting point:
Individual sellers (private sellers, sole traders)
UK limited company sellers
Higher-risk sellers (higher values, regulated or restricted categories, unusual payout patterns)
Non-UK sellers
A marketplace in Manchester sells second-hand cameras and new accessories. The same Saturday brings two applications. The KYS programme is the decision about which checks each one gets. KYC and KYB are the checks.
Priya wants to sell a used camera body. She is applying as a private seller. The programme asks for an identity document and a selfie, collects a proof-of-address document for a person to review if the category rules say so, and runs a sanctions and PEP screen. It does not ask her for a company number she does not have. If the document is readable and in date, the details match, the face match passes and the screen comes back clear, the check can be approved and she can list. If any of those is missing, she waits in the queue. The trust score on her report is a sorting aid for that queue. It is not the approval.
Northlight Imaging Ltd wants to sell new lenses. The application carries a company number. KYB starts at Companies House: is the company active, who are the directors, who is the person with significant control? The person who created the seller login is then checked as a person, the same way Priya was. A real company with an applicant who is not a director and not the person with significant control is not a pass. It is a question: is this person allowed to open the account? Someone on the marketplace's team answers it and records the answer. Screening covers the company and the key people, not only the login. UK registry checks and KYB are the product pages for that half of the flow. Seller verification is the page that puts the halves together.
Three weeks later Northlight's person with significant control changes. A check that ran on Saturday does not notice. Ongoing screening does, if the company and the people were enrolled. The alert goes to a person. The original approval is not silently rewritten. That is the third KYS question — should we keep trading — and it is why a one-time KYB at sign-up is not a programme. See ongoing monitoring.
The same marketplace later sells a high-value collector's lens. Identity and company checks do not hold the money. For that trade, escrow through Escrow.com, available on request. The check and the payment hold are different controls. Do not describe one as the other.
Payment partners and, where the platform rules apply, HMRC's reporting rules both end at the same practical test: can you show what you collected and why you let the seller trade? A useful record has the same shape every time.
| What you keep | Private seller | Limited company |
|---|---|---|
| Who was checked | The person | The company, the person opening the account, and the controllers you decided were in scope |
| Evidence | Document fields, face-match result, screen outcome | Companies House status, officers, people with significant control, plus the person's evidence |
| What did not run | Stated, not filled in as clear | Stated, not filled in as clear |
| Decision | Approved or held, with a reason if a person decided | The same, including why the applicant was accepted as acting for the company |
| Follow-up | Re-screen, and a fresh check if payout details change | Re-screen, and a fresh look if control of the company changes |
Review queues are where the held company cases are worked, with escalation when a second person should look. The engineering side of "what did not run" is in open-source signals.
Summary only, not legal advice. Which rules apply depends on your business model.
TrustVerify does UK seller and business verification for marketplaces in one place:
To compare plans, see our plans. Book a 30-minute demo below to see the seller flow end to end. For choosing a provider, read our guide to choosing KYC software in the UK.
KYC, KYB, AML screening and fraud prevention in one place, with published pricing.
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