Rules and ethics
How London marketplace agencies are evaluated against UK contract and data rules
Marketplace seller tools procurement in London needs UK contract law, ICO enforcement and CMA checks. Here is how to judge agency fees and exit terms.
What to take away
- Marketplace seller tools and agency contracts in London should be judged on written terms, data roles, fee transparency and exit mechanics, not on pitch decks.
- UK contract law sets the baseline: named parties, clear obligations, fair payment terms and remedies that survive termination.
- ICO enforcement shows that agencies handling customer data must have a lawful basis, a written processor agreement and breach notification duties.
- CMA guidance and the DMCC Act 2024 give you grounds to challenge unfair terms, drip pricing and poor marketplace conduct.
- Exit terms matter as much as onboarding: data export, account transfer, IP handover and a defined notice period.
- Ask for a data processing agreement, a fee schedule with no hidden commissions, and a named UK director accountable for delivery.
What UK contract law expects from a London agency agreement
A London agency agreement is a commercial contract. It does not need to be long, but it must identify the parties, the services, the price and the term. If those four things are vague, enforcement becomes expensive.
Agency agreements often mix a retainer with a commission on sales. Under UK contract law, a commission must be calculable from the contract itself or from records the contract requires the agency to keep. "Reasonable commission" is not a term a court can easily enforce.
Check who signs. An agency may present itself as a limited company, but the person signing must have authority. Director duties are personal, and a director who signs without authority can be liable. The government's guidance on being a company director sets out those duties, including acting within the company's constitution.
Payment terms matter. The late payment regime gives a statutory right to interest on overdue commercial debts, but the contract can set its own payment period. Thirty days is common; sixty days is a warning sign for a small seller.
Termination rights should be mutual. If the agency can terminate on 30 days but you are locked in for 12 months, that is a one-sided deal. Look for a break clause at six months and a notice period that matches the work involved.
Liability caps are standard, but they should not swallow the agency's core duties. A cap of the fees paid in the previous three months is common. A cap that excludes data breach liability entirely is not acceptable.
Governing law should be England and Wales, or Scotland if the agency is based there. A contract governed by a foreign law makes enforcement harder for a London seller.
For a broader view of how these clauses sit alongside software terms, see identity, money, audit and exit.
ICO enforcement signals on data handling by agencies
Most London marketplace agencies touch customer data: order details, addresses, email lists, returns. That makes them a processor for your business, and sometimes a controller for their own marketing.
The ICO expects a written contract between controller and processor. It must set out the subject matter, duration, nature and purpose of processing, the type of personal data, and the obligations of the processor. The UK GDPR guidance and resources | ICO explains those requirements in detail.
ICO enforcement has focused on direct marketing, cookies and breach response. An agency that runs email campaigns for you must have a lawful basis, usually consent or soft opt-in, and must honour opt-outs. If it buys lists, walk away.
International transfers matter. Many agencies use US-based tools for email, analytics or support. Transfers need a lawful mechanism, such as the UK extension to the EU-US Data Privacy Framework or the International Data Transfer Agreement.
Breach notification is a contractual point. The agency should notify you within 24 to 48 hours of becoming aware of a breach, so you can meet the 72-hour ICO deadline. If the contract says "promptly", that is too vague.
Sub-processors need control. The agency should not add a new sub-processor without notice and a right to object. Ask for a current list before signing.
Data retention should be defined. Customer data should be deleted or returned at the end of the contract, not kept "for backup" indefinitely. That links to exit terms, covered below.
A due diligence process that runs from identity to the terms of exit will surface most of these data issues before they become ICO complaints.
CMA guidance and the DMCC Act on marketplace conduct
The Competition and Markets Authority has been active on online marketplaces, from fake reviews to drip pricing. Its guidance and enforcement decisions set expectations for how sellers and their agents behave. The Competition and Markets Authority - GOV.UK page is the starting point for that work.
The Digital Markets, Competition and Consumers Act 2024, or DMCC Act 2024, changes the picture. It gives the CMA stronger powers on unfair commercial practices, including fake reviews and misleading pricing. The full text is on Digital Markets, Competition and Consumers Act 2024.
For a London seller, the DMCC Act 2024 matters in three ways. First, it makes drip pricing, where fees are added late, a clearer breach. Second, it targets fake and incentivised reviews. Third, it gives the CMA direct enforcement powers without going to court first.
Agency contracts should reflect this. If the agency runs promotions, it must substantiate claims and show total prices. If it manages reviews, it must not suppress negative ones or post fake ones.
The CMA also looks at how marketplaces treat sellers, including suspension and appeals. An agency that manages your Amazon UK or Etsy UK account should have a documented process for appeals and reinstatements.
Consumer law applies to your listings, and the agency is acting for you. A term that says the agency is not responsible for listing compliance is a red flag. Responsibility can be allocated, but it cannot be wished away.
Advertising claims about software or results need evidence. The Advertising Standards Authority can require substantiation, and the CAP Code applies to agency marketing as much as to yours.
Criteria for judging agency fees and accountability
Fees are where most London agency relationships go wrong. A clear fee schedule beats a low headline rate with vague extras.
Use this table to compare proposals. The criteria are drawn from UK contract law, ICO enforcement and CMA guidance.
| Criterion | What good looks like | Warning sign |
|---|---|---|
| Fee basis | Fixed retainer plus agreed commission, both stated | Percentage of "net revenue" undefined |
| Commission trigger | On dispatched orders, with returns deducted | On ordered value, returns ignored |
| Ad spend | Passed through at cost, with invoices | Marked up without disclosure |
| Reporting | Monthly, with source data | Screenshots only |
| Accountability | Named account director, UK-based | No named person |
| Data role | Written processor terms | No DPA offered |
| Exit | 30-day notice, data export included | Auto-renewal with 90-day notice |
Accountability is not just a name. It is a named person with authority to fix problems, plus a service level agreement with remedies. If the agency misses agreed response times, there should be a credit or a termination right.
Ask for a monthly reconciliation. It should show fees, ad spend, refunds and commissions in one place. If the agency cannot produce that, you cannot audit the relationship.
Check the agency's own company record at Companies House. Look at filing history, accounts and any charges. A healthy agency files on time and has no striking-off notices.
VAT treatment should be explicit. Most London agencies are VAT-registered, and their invoices should show VAT separately. If you are VAT-registered, you can usually reclaim it, but only with a valid VAT invoice.
Making Tax Digital affects how you keep records, not the agency's fees, but it does mean digital records should reconcile. Ask how the agency's reports feed your accounting software.
For a structured way to review these criteria, see how an agency review returns hold when the evidence is incomplete.
Exit terms and what a clean handover looks like
Exit terms are the most neglected part of an agency contract. They decide whether you can leave without losing sales history, listings or data.
A clean exit has four parts: notice, data, accounts and knowledge. Each should be written into the contract before you sign.
- Give notice in writing, using the method the contract specifies, and keep proof of delivery.
- Request a full data export in a usable format: CSV or the marketplace's own report files, not PDFs.
- Transfer account ownership, including marketplace seller central access, email tools and any domains registered in the agency's name.
- Get a written handover of campaigns, passwords, supplier contacts and pending cases, with a named person responsible for the transition.
Data export should be free. Some agencies charge a release fee. That is a term to challenge at the start, when you have room to negotiate.
Account ownership is critical. If the agency opened your Amazon UK or Etsy UK account in its own name, you may not control it. Insist that accounts are in your company's name from day one.
Intellectual property should be assigned. Listings, images and copy created by the agency for you should belong to you on payment. A licence that ends with the contract is not enough.
Notice periods should be short enough to be practical. Thirty days is common. Ninety days with auto-renewal is a trap.
Use this checklist before signing any exit clause:
- Notice period stated, with the method of notice
- Data export defined by format and deadline
- Account ownership in the seller's name
- IP assignment on payment
- No release fee for data or accounts
- Handover period with named contact
- Survival of confidentiality and data terms
Questions to put to a London agency before signing
Who is the named account director, and are they employed or contracted? Ask for the person who will run your account, not the sales lead. If they are a contractor, find out who supervises them.
Will you sign a data processing agreement with breach notification within 24 hours? This is an ICO expectation and a practical safeguard. If the answer is no, the agency is not ready for UK work.
How is commission calculated, and when is it deducted? Get the formula in writing, including how returns, refunds and cancellations affect it. "Net revenue" must be defined.
Which marketplace accounts will be opened, and in whose name? Accounts should be in your company's name. If the agency insists on its own name, treat that as a serious risk.
What happens to listings, images and data if we leave? You want an export in a usable format, an IP assignment and a handover period. Get the deadline in the contract.
Can you show your Companies House filing history and last accounts? This is a quick check on whether the agency is solvent and compliant. A refusal is a signal.
Common questions
Does UK contract law require a written agency agreement? No, a contract can be formed verbally or by conduct. But written terms are far easier to enforce, and data processing rules effectively require a written agreement anyway.
Who is liable if an agency mishandles customer data? The agency is liable as processor for its own failures, and you remain accountable as controller to the ICO. The contract should set out indemnities and breach notification duties.
How long should an agency notice period be? Thirty days is common and practical for most London retainers. Anything beyond 90 days with auto-renewal should be challenged before signing.
What should an exit data export include? Order history, customer records, campaign data, listing content and account credentials, in CSV or the marketplace's own report formats rather than PDFs.
Do CMA rules apply to small London agencies? Yes. CMA guidance and the DMCC Act 2024 apply to commercial practices regardless of agency size, including pricing, reviews and promotions run on your behalf.