Tools and providers
Part of Why out of home advertising tools and providers need a buying framework
What out of home advertising vendor due diligence means for buyer sign-off
A checklist for out of home advertising vendor due diligence: company records, compliance evidence, platform capability and the audit trail behind sign-off.
What to take away
- Format naming has changed as industry portfolio guidance was updated, so a rate card no longer proves what a screen can do.
- Due diligence now rests on company records and platform documentation, because buyers must show how a vendor was chosen.
- Match the legal entity on the Companies House register before you accept a trading name.
- Keep the vendor's compliance evidence separate from your own CAP Code duties, which sit with the advertiser and agency.
- Record each check in a dated file so sign-off can be repeated.
Check the vendor before the rate card
Confirm the legal entity and ownership
Start with the registered company. Match the legal name, company number and registered office against the name on the contract. Trading names, group brands and special purpose vehicles often differ, and a mismatch is a reason to pause rather than tidy later.
Ask who owns the company and whether a parent sits above it. Ownership changes can alter service levels, credit terms and control of the inventory. A short written answer shows whether the vendor knows its own structure.
Read the financial and credit signals
Request filed accounts and check the filing history for late submissions or changes of auditor. A vendor under pressure may still deliver, but the risk lands on your campaign dates.
Set a credit limit that reflects the exposure. For example, a team committing £18,000 a month over a year carries more risk than a one-off £4,000 test. Where the terms do not fit, agree milestones or staged payments.
The out of home advertising tools and supplier guide for 2027 shows where these checks sit beside pricing and inventory questions.
Test the inventory and the platform
Verify sites, formats and audiences
Ask for the site list, the format types and any audience data used to price the space. Where digital screens are involved, confirm scheduling and reporting capability against the platform documentation. The Microsoft Advertising developer resources set out what the buying interface returns, so you can test whether a vendor's reporting claims are plausible.
Check the vendor's format definitions against current industry guidance. The IAB UK note on the online ad portfolio explains how digital formats are defined, which helps you spot an old specification sold under a new label.
Check compliance evidence, not promises
Advertising content must comply with the CAP Code, and that duty sits with the advertiser and agency. The ASA advice for businesses explains those general obligations, out-of-home work included.
Ask the vendor for its content review process, approval records and any upheld complaints. A vendor that cannot describe its process passes that risk to you.
Build the sign-off file
Record what you checked and when
Keep a dated summary covering the company number, ownership, accounts reviewed, the site list version and the compliance evidence. That paper trail supports a procurement decision months later, and it is what finance teams ask to see.
Assign one named owner. Due diligence fails when it is spread across three inboxes.
Set review triggers and renewal points
Due diligence is not a one-off. Set triggers for a repeat check: an ownership change, new inventory, a shift in platform or reporting, or spend above the agreed credit limit. Put the next review date in the contract calendar.
When the vendor's tooling changes, the handover work matters as much as the checks. The guide to out of home advertising tool implementation covers the testing that follows a positive review.
| Check | Evidence to request | Owner |
|---|---|---|
| Legal entity | Companies House record and company number | Procurement |
| Ownership | Written structure note | Procurement |
| Financial standing | Filed accounts and filing history | Finance |
| Inventory and formats | Site list and format definitions | Media planning |
| Platform capability | API or reporting documentation | Media operations |
| Compliance | Content review process and complaint history | Legal or compliance |
Common questions
How long should out of home advertising vendor due diligence take?
For a standard campaign, allow two to three weeks from request to sign-off, depending on how quickly accounts and site lists arrive. Complex digital inventory takes longer.
Do I need to recheck a vendor every year?
Not always. Recheck when a trigger occurs, such as an ownership change, new inventory or a material rise in spend.
Who is responsible for CAP Code compliance?
The advertiser and agency carry responsibility for content compliance, not the vendor. The vendor should still evidence its own review process, because that supports your position if a complaint is made.
What if the vendor trades under a name only?
Find the registered entity behind it before signing. If no matching company record exists, ask for the parent entity and check that instead.
