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Affiliate marketing vendor due diligence without the guesswork
Checklist for UK retailers assessing affiliate marketing vendors: commercial proof, tracking reliability, compliance, data protection and a scoring rubric.
What to take away
- A Manchester retailer choosing between three networks should score each vendor on the same rubric, not on the polish of the sales deck.
- Ask for tracking evidence, a client reference and a data processing agreement before any pilot starts.
- Check how the vendor handles disclosure rules, because the Advertising Standards Authority treats affiliate content as advertising.
- Price the whole contract, including setup, minimum fees and overage charges, not just the headline commission rate.
- Keep a written record of what you checked, so the decision survives a change of marketing lead.
Start with the commercial basics
Due diligence begins with the contract, not the platform tour. Request the last two years of audited accounts or, for a private company, filed accounts from Companies House. Confirm the legal entity name matches the invoice and the data processing terms.
Ask what happens to your tracking links and historical data if the contract ends. A vendor that cannot answer in writing is a risk you carry into every campaign.
The Office for National Statistics reported that retail sales volumes across Great Britain rose by 1.7% in January 2025 compared with the previous month, which is the kind of figure a vendor may quote when pitching growth. Ask them to show how that demand translates into tracked sales for clients like you.
Test the tracking before you trust it
Attribution errors cost money quietly. Ask for a sandbox account and run a test transaction through your own checkout. Check whether the vendor records the click, the order and the cancellation correctly.
Request a sample reconciliation report. It should show clicks, orders, approved commissions and reversals in one view. If the vendor cannot produce one, you will be rebuilding it yourself.
For a wider view of how platforms compare on these operational points, the affiliate marketing tools and supplier guide for 2027 sets out the questions worth asking at each stage.
Check compliance and disclosure
The Advertising Standards Authority publishes specific guidance on affiliate marketing disclosure, including the need for affiliate content to be obviously identifiable as advertising. Ask the vendor how their publisher onboarding enforces this.
If your programme sells into the EU from Northern Ireland, VAT treatment changes. GOV.UK explains how to report and pay VAT on distance sales from Northern Ireland to the EU, which affects how commissions and invoices are structured.
Review data protection and security
Ask for the vendor's data processing agreement, sub-processor list and breach notification timeline. Confirm where personal data is stored and whether transfers leave the UK.
Check access controls. Who inside the vendor can see your customer data, and how is that access logged? A short written answer is enough at this stage.
If you are comparing shortlisted platforms in more detail, affiliate marketing software selection in England walks through the technical checks that sit alongside this commercial review.
Score every vendor the same way
Use a simple rubric so the comparison is defensible. Score each line from one to five and weight the categories to suit your programme.
| Category | What to check | Weight |
|---|---|---|
| Commercial | Pricing, minimum fees, exit terms | 20% |
| Tracking | Test transaction accuracy, reconciliation | 25% |
| Compliance | Disclosure enforcement, publisher vetting | 20% |
| Data protection | DPA, sub-processors, breach process | 15% |
| Support | Response times, named contact, onboarding | 10% |
| Roadmap | Release history, integration plans | 10% |
A vendor scoring below three on tracking should not proceed to pilot, whatever the commercial terms look like.
Documents to request before signing
- Filed accounts or audited financials for the last two years.
- A sample reconciliation report showing reversals.
- The data processing agreement and sub-processor list.
- Two client references, ideally from retailers of a similar size.
- A written exit plan covering data export and link migration.
Common questions
How long should vendor due diligence take?
For a mid-market retailer, two to four weeks is typical. Most of that time goes on the tracking test and reference calls, not the paperwork.
Do I need a pilot before signing a full contract?
Yes, where the vendor offers one. A thirty-day pilot on a single campaign gives you real tracking data at low cost.
What if the vendor refuses to share a data processing agreement?
Treat that as a failing score. You cannot lawfully process customer data without agreed terms, so the conversation ends there.
Should commission rate decide the shortlist?
No. A low rate on unreliable tracking costs more than a higher rate with clean attribution, because you pay twice for the same sale.
