Principal media disclosure clause: what to put in the contract

The clause points an advertiser should ask for on principal media, based on ANA and ISBA guidance from 2024 to 2026: approval per buy, a cap, no co-mingling and a working audit right.

A principal media disclosure clause is the part of your agency contract that stops the agency from selling you media it bought for itself, unless it labels the buy, explains it and gets your written approval first. The strongest version, in the ANA's own template, requires approval per transaction from named senior people, sets a cap, and treats any unapproved principal buy as fully transparent with no markup. If your contract says nothing, the agency decides.

For how principal media works and why it is spreading, read Principal media, explained for the people who sign the invoices. This post is about the paper. What follows is a set of plain-English clause points to brief your lawyer with. It is not legal advice, and your counsel should draft the final wording.

What the industry bodies have published

Three documents matter, and they point the same way.

ANA, May 2024. The report "The Acceleration of Principal Media" defined the model as agencies buying inventory at bulk rates and reselling it to clients at a markup. Its recommendations: keep agency contracts current with clear language on principal media, make the agency justify each recommendation against your media strategy, ask for options that don't use principal media, set an internal approval process, label principal media on flowcharts, and require the same proof of performance and transaction data as agent-based buys.

ANA, March 2026. "The Continued Acceleration of Principal Media (and the importance of proper governance)" surveyed 114 client-side marketers. 58% had used principal media in the past year, up from 47% in 2024. Only 63% said their agency contracts address it, and more than a third said their contracts don't or they aren't sure. The report goes further than 2024. It tells marketers to forbid co-mingling of principal and agent buys, to consider a cap on principal media as a share of budget, to require business cases with cost and audience delivery compared against agent-led buys, and to make sure pitch pricing guarantees cover only agent-based buys. It also reprints section 9 of the ANA and Reed Smith Master Media Buying Services Agreement Template (version 3.0), which is the closest thing the US market has to standard clause language.

ISBA, February 2026. The UK advertiser body published guidance on what it calls proprietary media. Marketing Week's summary of it lists the same moves: define it clearly within media plans, secure granular data, consider spend limits, exclude it from pitch guarantees, and update contracts.

Two advertiser trade bodies on two continents landing on the same list is the signal. This is now standard governance, not a niche ask.

The clause, point by point

1. Define it broadly. Any transaction where the agency or an affiliate buys media in its own name and resells it to you, whatever the product is called. The ANA template uses the term "non-transparent services" and requires the agency to label them clearly without relying on affiliate brand names alone. That matters, because principal products usually arrive under a trading desk brand, not under the word "principal."

2. The default is no. Principal buys are prohibited unless approved in writing, in advance, for each instance. The ANA template names the CMO and the head of marketing procurement as approvers. Approval of a media plan, a purchase order or a flowchart does not count as approval of the principal buys inside it.

3. Specify what the approval request must contain. Under the template, the agency's request states the cost, timing, media type, impressions and KPIs; the maximum cost as a share of each media type; the transparent alternatives it looked at and why this option is better; the percentage of your annual spend already committed to principal buys; any rebates or incentives you give up; cancellation charges; and any limits on data or record access.

4. Set a cap. No more than a fixed percentage of total budget for a defined period. The ANA 2026 report suggests exactly this. Pick a number you are comfortable defending to your CFO.

5. No co-mingling. Principal and agent buys stay separate, and the agency confirms that no value moved between them. Budget can't shift from agent to principal buys without your authorization.

6. Same proof of performance, same safety rules. Invalid traffic, viewability, brand suitability, impressions, clicks and outcomes, reported the same way as everything else. Your block lists, inclusion lists and verification tags apply.

7. Reporting you can reconcile. A monthly written report of principal amounts by channel, delivered within a fixed number of days after month end.

8. An audit right that still works. You can audit principal buys like agent buys. The ANA's version is a fair compromise: the agency reveals what it charged you, with pricing detail rather than totals, but not what it paid the vendor.

9. Keep it out of the scorecard. Principal buys don't count toward agency KPIs or performance compensation unless you agree in writing. Pitch savings guarantees apply to agent buys only.

10. A remedy for unapproved buys. If the agency makes a principal buy without approval, you either don't pay for it or it is treated as fully transparent, with audit, data and rebate limits voided. You pay no more than the lower of actual net media cost or the approved amount.

11. A warranty with teeth. The agency warrants that the recommendation fits your strategy and serves your interest, and that the cost doesn't exceed a disclosed traditional buy unless the difference is disclosed and agreed.

12. The contract wins. Contract terms prevail over anything in a purchase order or authorization form. Changes happen in the contract, nowhere else.

Where agencies push back

The margin. Nothing above forces the agency to disclose what it paid for the inventory, and most won't. That is the trade you are making: you give up seeing the markup, and in return you get a priced comparison against the open market, per-buy approval, a cap and a working audit right. In our view that is a fair trade. Insisting on full margin disclosure usually ends with the product withdrawn, which costs you access to inventory that was good value.

The other pushback is speed. Agencies will say per-buy approval slows down scatter buys. Fine. Pre-approve a category with a ceiling (last-minute TV scatter up to a set amount, for example) and keep per-buy approval for everything else.

Do this before the next pitch or renewal

Pull your current master services agreement and search it for "principal," "proprietary," "non-transparent," and the names of your agency's trading products. If none of them appear, the points above go into an amendment now, not into the next pitch. If you want a second read on the language you already have, our Second Opinion covers a single contract in five business days, and the wider agency relationship is covered under marketing cost.

Sources: ANA, With principal media on the rise, ANA report seeks to educate marketers on best practices (May 2024), ANA, Governance around principal media failing to keep pace with industry adoption (March 2026), ANA, The Continued Acceleration of Principal Media (2026 report), Marketing Dive, Principal media buying: how marketers can safeguard themselves, per ANA, ISBA, New guidance on proprietary media (February 2026), Marketing Week, ISBA launches guidance on how brands can approach proprietary media.