Before you sign a connected TV advertising vendor, run this due diligence check

What to take away

Most teams check price and reach first, then find the vendor cannot evidence where impressions ran or who sold the inventory.
Ask for the registered company name, company number and address before any commercial conversation, then verify each one.
Get the measurement method in writing, including what counts as a completed view and who validates it.
Check data protection terms, sub-processors and retention periods while the contract is still a draft.

Ownership and inventory

Verify who you are actually buying from

Trading names hide group structures. Ask for the registered company name, company number and registered address, then check the filing history and accounts on the Companies House register. Overdue accounts or a recent name change deserve a follow-up question.

Vendor ownership and supply path checks

Registered company name and number
Filing history and accounts checked
Inventory owner named in writing
Supply chain declaration requested
Direct, programmatic or mix share

Ask who owns the inventory. A reseller, an aggregator and a broadcaster-owned platform carry different risks when a channel drops out mid-campaign. Get the answer in writing, naming the platforms and the contract terms behind them.

Check the supply path

Request the supply chain declaration for the domains you expect to buy. If the vendor cannot say which intermediaries sit between your budget and the publisher, you cannot assess fraud exposure or brand safety.

Ask whether inventory is direct, programmatic or a mix, and what share of each. For a wider view of these arrangements, the connected TV advertising supplier comparison sets out the trade-offs between managed, self-serve and hybrid models.

Measurement and reporting

Agree what a view means

Definitions vary. One platform counts a completed view at 100 per cent of the creative, another at 97 per cent, and some count a few seconds. Ask for the exact threshold in the insertion order, not in a slide.

View definitions vary by platform

Platform A

Completion threshold: 100 per cent
Verification: Independent body
Reporting fields: Device, app, region

Platform B

Completion threshold: 97 per cent
Verification: Self-reported
Reporting fields: Completion rate

Platform C

Completion threshold: A few seconds
Verification: Self-reported
Reporting fields: Missing fields

Ask which independent body verifies the numbers. If the vendor self-reports only, plan your own verification, such as a matched control group.

Test the reporting before you scale

Request a sample report with the fields you need, including device, programme or app, region and completion rate. If the sample lacks a field, assume it will be missing at month end.

Set a reconciliation routine. For example, a team paying £18,000 a month for streaming ads might reserve £1,500 for independent verification, then compare platform-reported impressions with the verification tag before renewing.

Contracts, data and exits

Data protection and audience data

If the vendor processes personal data, you need a data processing agreement, a sub-processor list and retention periods. Check whether audience segments come from first-party data, licensed data or modelled estimates, because that changes your lawful basis.

Ask where data is stored and whether it leaves the UK. Under the UK GDPR, international transfers need a valid mechanism.

Audit rights and termination

Ask for an audit right, even a limited one, plus the right to see the supply chain declaration annually. Suppliers often accept this once commercial terms are agreed.

Check notice periods, minimum spend commitments and what happens to creative assets and data on exit. A 90-day notice on a rolling annual deal is worth flagging to finance early.

Putting the checklist to work

Run the checks in order: company verification, supply path, measurement definition, reporting sample, then contract terms.

Keep a written record of what the vendor told you and when. If a claim changes before signature, that gap is the finding.

For platform detail, Microsoft Advertising's ad products documentation explains how its video and connected TV formats are bought, and LinkedIn's advertising documentation covers its video formats and targeting. If your plan includes social video, TikTok Ads Manager's catalogue help page sets out how product catalogues are created for video campaigns.

The connected TV advertising tools and supplier guide maps the wider supplier categories, so you can see which checks matter most for your model.

Common questions

How long should vendor due diligence take?

For a mid-sized campaign, allow two to three weeks. Company checks take a day, but measurement definitions and contract terms usually need two rounds of written questions.

What if the vendor refuses an audit clause?

Ask why in writing. A refusal on a small-spend deal may be proportionate, but a refusal on a six-figure commitment is a signal to walk away.

Do I need this for a small test budget?

Yes, but scale it. Verify the company, get the view definition in writing and confirm who owns the inventory. Leave the audit clause for the renewal conversation.

Which clause causes the most disputes?

Notice periods and minimum spend commitments. Both are easy to overlook in a pitch and hard to change once the campaign is live.