How to audit your agency's programmatic buys: contract rights, data, benchmarks and a ten-step plan

An audit has three layers. Each needs different evidence, and each can fail on its own. An agency can follow the contract to the letter and still buy poor media; it can buy excellent media through a path the contract never allowed.

The layers interact. A fee that looks fair can hide poor media, because a low platform fee on invalid traffic is still money wasted. A strong quality score can hide a billing gap, because good impressions bought through an unapproved markup still cost too much. Report each layer separately before you combine them. The ANA benchmark combines the second and third layers into one number, TrueAdSpend. What it counts and leaves out is explained in working media vs non-working media.

An audit can only test what the contract lets you see. Read the agreement first. The ANA's media agency contract template, written with the law firm Reed Smith, was first issued in July 2016 and updated on 11 July 2018 (ANA). Its clauses are a useful checklist even if your contract uses other wording.

The template's definitions of value pots and transaction data, and the NDA recommendation, come from the ANA's summary of its 2018 update (ANA). Rebates and kickbacks as a contracting topic are covered in media agency rebates and kickbacks.

Advertisers in the UK and Europe often start from a different template. The ANA built its master media buying agreement with permission to use the framework of ISBA, the UK advertisers' association, and its counsel Fieldfisher (ANA). The two documents share the same core ideas: audit access, disclosure of non-transparent buying and ownership of rebates. Whichever you use, check that the clauses survive into the statements of work, where fees are often changed.

When an agency buys as your agent, it passes media costs through and earns a disclosed fee. When it buys as principal, it buys inventory on its own account and resells it to you at a price it sets. The margin is not disclosed, and a standard audit cannot see it.

Principal buying is not banned or always bad. The ANA's 2026 study found that 76% of marketers cite reduced costs as its main benefit (ANA, 19 March 2026). But the same study found only 63% of contracts address it, and more than a third of marketers say theirs do not or are unsure. The ANA's chief executive put the test simply: marketers should always understand "whether their agency is acting as an agent or a principal in any media transaction".

For the audit, the consequence is practical. Agent buys can be reconciled line by line against platform costs. Principal buys can only be tested on price and quality, by comparing what you paid per quality impression with agent-based buys of similar media. Ask the agency to flag every principal buy before the audit starts. If it cannot, sample invoices for media vendors you know sell through principal arrangements, and ask how each line was bought.

Send the request early. Some platform data expires, and gathering it from several companies takes weeks. The table works as the core of a request letter.

DSP fees deserve a careful look. The Trade Desk, for example, charges "a platform fee generally based on a percentage of our clients' total spend on our platform" (The Trade Desk, 10-K for 2025). Its revenue of $2,896.3 million on gross spend of $13,394.7 million implies an average take rate of 21.6% in 2025. Your contracted rate may differ; what each line means is set out in The Trade Desk fees explained. How log files arrive and how to store them is covered in log-level data.

Numbers mean little without a yardstick. The ANA's quarterly benchmark, run with TAG TrustNet and Fiducia, is the most complete public one. It is built from participants' log-level data matched across DSPs and verification vendors.

The ANA had not published its Q3 2026 benchmark when this page was last updated; the ANA press room showed Q1 2026 as its latest programmatic release. The full series, quarter by quarter, is in the working media benchmark. The 2023 study adds a sense of scale: the ANA put the efficiency gains available to marketers at $22 billion (ANA).

Use the benchmark with care. The ANA leaves agency fees outside its waterfall, so add your agency fee on top before you compare. And compare like with like: a CTV-heavy plan should be compared with the all-environment series.

You have three options, and the choice affects what the audit can find. An internal team knows the business and costs little, but agencies may refuse to share commercially sensitive data with a client's staff. An independent media auditor brings benchmarks from other clients and can sign the NDA the agency expects. A specialist programmatic auditor adds the data engineering needed to join log files across platforms.

Independence matters more than the brand of the auditor. The firm should not sell media, technology or consulting to the same agency, and its fee should not depend on the size of the money it claims to find. Ask who will see the raw data, where it will be stored and when it will be deleted. Those answers belong in the engagement letter.

Many advertisers mix the options. An external firm runs the first full audit and sets up the reconciliation model. The internal finance team then runs the monthly checks, and the external firm returns once a year. Whatever the mix, one person on the advertiser's side should own the audit and its follow-up, with authority to request data from every vendor.

An audit goes faster when the advertiser can answer its own questions. Before the request letter goes out, collect four things.

1. The signed contract and every amendment. Statements of work often change fees without changing the master agreement.
2. Your own payment records. Finance can list every payment to the agency by month; that list is the anchor of the reconciliation.
3. The approved media plans. Plans show what was agreed: channels, budgets, quality targets and any principal buys you approved.
4. A list of platform logins. Note which DSP seats, ad server accounts and verification dashboards are in your name. Anything in the agency's name needs an export request.

If the seat is in your name, you can often pull fee reports and log-level files yourself. That shortens the audit by weeks, and it shows the agency that the data request is a formality rather than a fishing trip.

The plan below assumes a mid-sized advertiser and an external auditor. The weeks are a guide; large accounts take longer.

1. Week 1: read the contract. List audit rights, the NDA, agent and principal terms, rebate definitions and data rights. Note every gap.
2. Week 1: send the data request. Use the table above. Ask for log-level files first, because some expire after 60 days.
3. Week 2: agree scope and period. Pick a period of three to six months, the platforms in scope and the quality standards (for example the ANA's TrueImpression definition).
4. Weeks 2 to 3: sign the auditor NDA. Use the exhibit in your contract if there is one. Resist terms that let the agency approve the findings.
5. Weeks 3 to 5: reconcile money. Match agency invoices to DSP invoices, then DSP invoices to log-level cost, month by month.
6. Weeks 3 to 5: classify fees. Split media cost, DSP platform fees, data fees, ad serving, verification and agency fees. Flag anything unlabelled.
7. Weeks 4 to 6: test quality. Join log-level data with verification logs. Measure invalid, unmeasurable, non-viewable and MFA spend.
8. Weeks 4 to 6: review supply paths. Count domains, apps, SSPs and resellers; look for duplicate paths and curator fees. Buyers' supply path optimization work starts here.
9. Week 6: check principal buys and rebates. Compare principal-bought media on cost per quality impression with similar agent-bought media; reconcile rebate statements.
10. Weeks 7 to 8: report and decide. Present findings by layer, with the money at stake for each, and choose actions from the decision table below.

All numbers in this example are illustrative. An advertiser is billed $1,000,000 for October programmatic media. The contract says the agency acts as agent, passes platform costs through and charges a separate fee. The steps follow the audit plan: invoices first, then log-level data.

The DSP's invoices to the agency for October total $925,000. Log-level data shows $660,000 of media cost paid into auctions, $185,000 of DSP platform fees, $55,000 of data fees and $25,000 of verification and ad serving. Those four lines add up to the $925,000 invoiced, the same split of media, platform and data fees described in the ad tech tax explained. That leaves $75,000 between the agency's bill and the platform's invoice.

The audit asks the agency to explain the gap. Three answers are common: an undisclosed trading desk fee, a principal buy at a marked-up price, or a timing difference between months. Only the last is acceptable under this contract, and it should reverse the following month.

Then the quality layer. Verification logs show that $280,000 of the $660,000 media cost bought impressions that were valid, measurable, viewable and not on MFA sites. That is 28% of the $1,000,000 billed, below the ANA's lower-performer level of 31.1% in Q2 2026 (Fiducia on ANA). The audit has found two problems: an unexplained 7.5% gap, and media quality in the bottom group. To model the fee lines in your own account, use the ad tech fee calculator.

The ANA's media transparency recommendations, prepared with Ebiquity and FirmDecisions, say advertisers should insist on broad audit rights that cover both contract compliance and the media value delivered (ANA). If you meet resistance on any red flag, that recommendation is the reference point.

A single audit fixes the past. A routine keeps the problems from returning. Build three habits from the audit's own tools.

Monthly: reconcile the agency invoice against platform invoices and log-level cost, using the model the audit built. Investigate any gap above an agreed threshold within the month, while the files still exist.

Quarterly: compare your quality share and fee share with the latest ANA benchmark, and review the domain and app list. A list that grows by thousands of sites a quarter is a sign that inclusion rules have slipped.

Yearly: run the full audit again, with the same scope, so results can be compared. Review the contract against the audit's findings and the latest ANA guidance before renewal.

Put the routine in the contract. An agency that knows invoices are reconciled every month has little reason to bundle fees, and one that knows the audit will repeat has every reason to fix what the last one found.

An audit ends with a decision, not a report. The table maps the most common findings to the action that addresses them. It is our framework, built from the steps above.

Three outcomes are common. Some advertisers keep the agency and fix the contract. Some keep the agency for planning but own the platforms and data. Others build a trading team, often after a second audit shows the same problems. The three operating models, with roles and costs, are compared in the in-house programmatic operating model. How the fee chain adds up across every hop is in the ad tech tax explained.

1. ANA, "Programmatic Media Supply Chain Transparency" hub, on the December 2023 study and benchmark (accessed 9 November 2026). https://ana.net/programmatic
2. Fiducia, "ANA Programmatic Transparency Benchmark: Q2 2026 Working-Media Efficiency Reaches a Record 45%" (6 August 2026). https://www.fiducia.eco/post/ana-programmatic-transparency-benchmark-q2-2026-working-media-efficiency-reaches-a-record-45
3. ANA, "ANA Study: Governance Around Principal Media Failing to Keep Pace With Industry Adoption" (19 March 2026). https://www.ana.net/content/show/id/pr-2026-03-principalmedia
4. ANA, "Media Transparency: Prescriptions, Principles, and Processes for Marketers, Overview", including the updated media agency contract template (11 July 2018) and the K2 Intelligence study findings (accessed 9 November 2026). https://www.ana.net/content/show/id/industry-initiative-recommendations-overview
5. ANA, Press Room (checked 9 November 2026 for the Q3 2026 benchmark). https://www.ana.net/content/show/id/pressroom
6. Google for Developers, "Display & Video 360 and Campaign Manager 360 Data Transfer v2.0 overview" (last updated 14 October 2024). https://developers.google.com/bid-manager/dtv2/overview
7. The Trade Desk, Inc., Form 10-K for fiscal year 2025 (filed 27 February 2026). https://www.sec.gov/Archives/edgar/data/1671933/000167193326000014/ttd-20251231.htm
8. PPC Land, "Publicis and The Trade Desk make up as ad tech's trust layer cracks" (13 June 2026). https://ppc.land/publicis-and-the-trade-desk-make-up-as-ad-techs-trust-layer-cracks/