Loading page...
Loading page...
Understanding the hidden costs in your media supply chain and how to ensure complete transparency across every pound of your advertising investment.
Media transparency refers to the practice of full, open disclosure in all aspects of the advertising supply chain — from how media is bought and at what cost, to where ads are placed, what fees are charged, and whether any undisclosed commercial arrangements exist between parties. It is the principle that advertisers should have complete visibility into how their media investment is being managed and where their money goes.
No hidden markups, no undisclosed commercial arrangements, and no conflicts of interest that could compromise the objectivity of media buying decisions.
The reality, unfortunately, often falls well short of this ideal. The UK advertising market — worth over £35 billion annually — has faced persistent transparency challenges. The Association of National Advertisers (ANA) in the US and industry bodies in the UK have both published landmark studies revealing significant opacity in media trading practices.
Industry research into the programmatic supply chain has found that approximately 15% of advertiser spend in the programmatic supply chain could not be attributed to any identified party — it simply disappeared into the "unknown delta."
For marketing leaders and CMOs, understanding media transparency is not merely an ethical concern — it is a financial imperative. Lack of transparency directly erodes return on investment, and the sums involved can be substantial. Understanding where the risks lie is the first step towards protecting your investment. If you are new to media auditing, our guide on what media auditing involves provides a comprehensive introduction.
12–30%
of media budgets lost to hidden costs
£1.2M–£3M
potential loss on £10M annual spend
15%
of programmatic spend unattributable (industry research)
Beyond the direct financial impact, a lack of transparency creates a trust deficit between advertisers and their agencies. When agencies operate without full disclosure, it becomes impossible for brands to evaluate whether their partners are acting in their best interest. Are media buying decisions driven by what is best for the advertiser, or by what generates the highest margin for the agency? Without transparency, this question cannot be answered.
The UK advertising industry has made meaningful progress through the efforts of industry bodies representing both advertisers and agencies. Framework agreements set standards for agency-client contracts, including provisions for transparency and disclosure. However, adherence varies widely, and many contracts still permit agencies to retain rebates or charge undisclosed fees.
The UK's Competition and Markets Authority (CMA) has examined competition concerns in digital advertising markets. The Digital Markets, Competition and Consumers Act provides new powers to address transparency issues. Meanwhile, the Advertising Standards Authority (ASA) continues to enforce rules on misleading advertising, though its remit does not extend to the commercial terms between agencies and advertisers.
For brands seeking to take control of their media investment, an independent agency contract review is one of the most effective first steps towards achieving meaningful transparency.
Through our experience auditing media agency relationships across dozens of engagements, we consistently encounter the same categories of hidden costs. Understanding these is essential for any advertiser seeking to protect their investment.
Volume bonuses from media owners retained by agencies are perhaps the most well-known transparency issue in the industry. Media agencies that place large volumes of spend with specific media owners often receive volume rebates -- essentially a discount for bulk buying. The question is: who benefits from that discount?
In a transparent relationship, these rebates are passed through to the advertiser, reducing their effective media cost. In opaque arrangements, the agency retains all or a portion of the rebate as additional revenue, often without the advertiser's knowledge.
In our audit experience, undisclosed rebates typically range from £80K to £300K annually for mid-to-large advertisers. In one notable engagement, we recovered £150K in hidden rebates for a travel brand that their agency had been retaining for over three years without disclosure.
Agencies buying media cheaply in advance and reselling it at a markup is a practice known as "inventory buying" or "principal buying." The agency purchases media space in bulk from publishers at discounted rates, then resells it to clients at higher prices -- effectively acting as a media reseller rather than a buying agent.
Whilst not inherently unethical, this practice becomes problematic when it is not disclosed to the advertiser. The key concern is that it creates a conflict of interest: the agency is incentivised to recommend media it owns (to maximise its margin) rather than the media that would deliver the best results for the advertiser. Markups on inventory media typically range from 15% to 40% above market rates, and the advertiser has no visibility into the actual cost paid.
Hidden fees in programmatic buying through agency trading desks represent one of the least transparent areas of modern media buying. When agencies operate their own trading desks to execute programmatic campaigns, they often add a markup on top of the DSP costs -- typically 10% to 20% of media spend -- which may not be clearly disclosed in contracts or invoices.
These markups are sometimes described as "technology fees" or "platform charges," making them difficult to identify without forensic analysis. For an advertiser spending £2M on programmatic media, a 15% undisclosed trading desk markup represents £300K annually in hidden costs. Our programmatic audit service specifically examines these arrangements.
Excessive markups on creative production are another common area of concern. Agencies frequently outsource production work to freelancers, studios, and production houses, then add their own markup before invoicing the client. Whilst a reasonable margin for project management is expected, markups of 40% to 60% above the actual production cost are not uncommon.
In one audit, we found that a social media video quoted to the client at £8,500 was actually produced for £3,200 by an external studio -- a markup of over 165%. Across a full year of production work, these markups can add up to £30K-£100K in unnecessary costs for mid-sized advertisers.
Opaque charges for proprietary tools and data have proliferated as agencies have invested in building their own technology platforms. Clients are increasingly charged for access to agency-owned tools for audience data, planning, attribution, and reporting -- often at rates that significantly exceed the actual cost of the underlying technology.
The challenge is that these fees are frequently bundled into overall media costs, making them difficult to isolate and evaluate. In our audits, we regularly find that 3-8% of total media spend is allocated to technology and data fees that provide questionable incremental value beyond what is available from standard platforms.
Undisclosed commercial relationships between agencies and media vendors, technology providers, or other service partners can create conflicts of interest that compromise the objectivity of agency recommendations. These arrangements may include referral fees, equity stakes, or preferential commercial terms that incentivise the agency to recommend specific partners.
For example, an agency might recommend a particular verification vendor, attribution platform, or research provider because of a commercial relationship rather than because it is genuinely the best solution for the client. Whilst these arrangements are sometimes disclosed in fine print, they are rarely proactively communicated.
Programmatic advertising deserves special attention in any discussion of media transparency because it is where the most significant opacity exists. The programmatic supply chain is deliberately complex, with multiple intermediaries between the advertiser's budget and the publisher's ad slot — each taking a fee along the way.
Research consistently shows that only 35% to 55% of programmatic ad spend actually reaches the publisher whose inventory displays the ad. The remaining 45% to 65% is consumed by intermediaries: DSP fees, SSP fees, data costs, verification charges, trading desk margins, and other supply chain participants.
For every pound you invest in programmatic advertising, only 35p to 55p is actually working to reach your audience.
A single programmatic impression can pass through 10 or more intermediaries before being served to a user. Each intermediary adds a layer of cost and opacity. The advertiser sees a reported CPM, but the actual breakdown of that cost between intermediaries is rarely visible. This complexity is not accidental — it benefits the intermediaries who profit from opacity.
The programmatic ecosystem has also given rise to ad fraud (where bot traffic generates false impressions and clicks) and made-for-advertising (MFA) sites — low-quality websites created solely to generate advertising revenue through clickbait content and aggressive ad placements.
MFA sites technically deliver "valid" impressions but provide near-zero brand impact or commercial value. Our audits typically find that 10–25% of programmatic display budgets are affected by fraud or MFA inventory.
Supply path optimisation (SPO) is the practice of identifying and using the most direct, cost-efficient routes to quality inventory. By mapping the programmatic supply chain and eliminating unnecessary intermediaries, advertisers can increase the proportion of their spend that reaches genuine audiences in quality environments. Our programmatic audit includes comprehensive supply path analysis as standard.
Achieving genuine media transparency requires a proactive, multi-faceted approach. Here are seven practical steps every advertiser should take to protect their investment.
Your agency contract should contain an explicit clause requiring disclosure of all rebates, volume bonuses, and incentives received from media owners in connection with your account. The clause should specify whether these are retained by the agency or passed through to you, and require regular reporting on the amounts involved. Ambiguous language like "commercially sensitive arrangements" should be challenged.
Insist on a clear, itemised breakdown of all agency fees -- management fees, technology charges, trading desk margins, data costs, and production markups. Each fee should be expressed as a specific percentage or fixed amount, not bundled into opaque "service charges." You should know exactly what you are paying for each element of the agency's service.
Contractual audit rights allow you (or an independent third party) to examine the agency's financial records relating to your account. This includes invoices from media owners, platform spending records, and documentation of any commercial arrangements. Audit rights are the single most powerful tool for ensuring ongoing transparency. Learn more about what to look for in our agency contract review service.
Regular, independent verification of actual media costs against reported costs is essential. This involves comparing what your agency reports as media expenditure against what was actually paid to media owners and platforms. Discrepancies between reported and actual costs are one of the clearest indicators of transparency issues. Our media audit service includes forensic cost verification as standard.
Agency contracts should be reviewed at least annually, not just at renewal. As your media spend grows, your terms should improve -- not remain static. Regular reviews ensure fee structures remain competitive, transparency provisions are being honoured, and performance obligations reflect current expectations. Many advertisers are surprised to find they are still operating under terms agreed when their spend was a fraction of its current level.
For advertisers with significant programmatic spend, supply path optimisation should be a priority. This involves mapping the routes your ads take through the programmatic supply chain and eliminating unnecessary intermediaries. Direct publisher relationships and preferred SSP paths can significantly reduce the "ad tax" and improve both transparency and cost efficiency.
Relying solely on your agency for performance measurement creates a fundamental conflict of interest. Independent measurement tools and attribution platforms ensure that performance data is objective and not influenced by the entity being evaluated. Consider implementing independent verification for viewability, brand safety, and audience delivery alongside your own analytics. Our media waste calculator can help you estimate the potential impact on your specific budget.
At Fuel Media, transparency is not just something we advocate — it is the foundation of everything we do. As a fully independent media auditor with no agency relationships, platform partnerships, or media buying interests, we have no conflicts of interest that could compromise our objectivity. Our only commercial interest is in delivering accurate, actionable insights for our clients.
In a recent engagement with a leading online travel agency, our independent review uncovered £150K in undisclosed rebates along with hidden trading desk markups and inflated production costs. In total, we identified £520K in annual savings.
Undisclosed rebates remain surprisingly common in the UK advertising industry. Industry research into the programmatic supply chain has found that a significant proportion of advertiser spend cannot be attributed to any identified party. In our experience auditing agency relationships, we find undisclosed rebate arrangements in roughly 60% of engagements. These typically range from 2% to 8% of total media spend, representing tens or hundreds of thousands of pounds annually for mid-to-large advertisers. The challenge is that rebates are not inherently problematic -- the issue arises when they are not disclosed to the advertiser, effectively creating a hidden revenue stream for the agency.
A robust agency contract should include several key transparency provisions. First, a comprehensive rebate disclosure clause requiring the agency to declare all volume bonuses, rebates, and incentives received from media owners -- and specify whether these are retained or passed through. Second, an explicit fee schedule detailing all charges including management fees, trading desk markups, technology fees, and production margins. Third, audit rights allowing you (or an independent auditor) to examine the agency's books, invoices, and trading records. Fourth, a conflict of interest disclosure policy requiring the agency to declare any ownership stakes, referral arrangements, or commercial relationships with media vendors. Industry best-practice frameworks provide a solid template for these provisions.
Auditing programmatic transparency requires a multi-layered approach. Start by requesting log-level data from your DSP, which reveals the actual cost paid for each impression and the supply path it travelled. Compare reported CPMs against actual clearing prices to identify any hidden markups. Map the complete supply chain from your budget to the publisher, documenting every intermediary and their fees. Assess inventory quality by reviewing domain-level placement reports and checking for made-for-advertising sites. Verify that ad fraud detection tools are properly configured and review invalid traffic rates. Finally, evaluate your supply path optimisation strategy to ensure you are buying through the most direct routes available. An independent programmatic audit typically uncovers 15-30% in efficiency opportunities.
The financial impact of poor transparency varies by advertiser size and media mix, but the numbers are typically significant. For a brand spending £5M-£20M annually on media, common hidden costs include: undisclosed rebates (£80K-£300K per year), trading desk markups (£50K-£200K), production cost inflation (£30K-£100K), and programmatic supply chain inefficiency (where only 35-55% of spend reaches publishers). In total, we typically find that 12-25% of total media investment is affected by transparency issues. For a £10M advertiser, that represents £1.2M-£2.5M in potential savings or recovered value. In our audit experience, we have recovered £150K in hidden rebates for one travel brand and identified £520K in total annual savings through comprehensive transparency improvements.
Complete guide to understanding media audits, types, process, and what makes a good auditor.
Read moreIndependent review of agency contracts to uncover hidden fees, unfavourable terms, and cost-saving opportunities.
Read moreGet an obligation-free assessment of your agency contract from our independent media auditing experts.
Read more