What is the ad tech tax, and where does the money actually go?
Part of Supply path transparency
The short answer
The ad tech tax is an informal name for the share of a programmatic budget that intermediaries keep before the publisher is paid: agency fees, DSP fees, data and verification costs, SSP fees and any spend no one can trace. It is not a government tax. Buyers measure it by matching their spend records to what the publisher received.
Key takeaways
- Fees enter on both sides of the auction: the buy side through contracts and platform charges, the sell side as shares of the clearing price.
- In ISBA's 2020 UK study publishers received 51 percent of advertiser spend on average, and 15 percent could not be attributed to anyone.
- Fees and waste are different problems; the ANA's Q1 2026 benchmark found media quality losses varied far more between advertisers than transaction costs.
- No public seller file or bid request field states an SSP's take rate; that needs the SSP's own revenue records.
- Fee transparency comes from contract terms, platform fee settings and log level data shared with permission.
What is the ad tech tax?
Definition
- Ad tech tax
- The combined cost of the companies between an advertiser's budget and a publisher's revenue, expressed as the gap between the two. The phrase is industry slang; no law or standard defines it.
The question behind the phrase is old and simple. In January 2018 ISBA's advertiser members asked, in the words of its later report, "what does my programmatic supply chain look like and how can I assess its value in terms of working media?" Answering it took PwC two years of contracts, permissions and data matching, according to the ISBA programmatic supply chain transparency study (opens in a new tab) published in May 2020.
Where do fees enter a programmatic buy?
Google's Display & Video 360 help page on fees and billable cost (opens in a new tab) shows the buy side layer clearly. It defines media cost as "The raw cost incurred for purchasing impressions" and the platform fee as "The charge for using the platform to serve your ads, calculated as a percentage of the Media Cost," with rates set in the contract and visible under Partner settings. Platform add on fees and third party fees sit on top. Agency and partner markups entered as partner costs "only appear in reporting and will not show up on your invoice."
| Layer | Who charges it | How it is set | Where the buyer can see it |
|---|---|---|---|
| Agency fee or markup | The agency or trading desk | Agency agreement: fixed fee, commission or markup | The agreement; DV360 partner costs show in reporting, not on the invoice |
| DSP platform fee | The buying platform | Contract rate, a percentage of media cost in DV360 | Platform fee settings and invoices |
| Data, ad serving, verification | Third party providers | Their own rate cards, billed through or beside the DSP | Fee columns in platform reports and supplier invoices |
| Exchange or SSP share | The exchange that ran the auction | Seller contract with the publisher, taken from the clearing price | Not in buyer reports; needs SSP or publisher data |
| Reseller or sales house share | Each intermediary seller in the chain | Its agreement with the publisher or the upstream seller | Not in buyer reports; the chain shows the party, not the amount |
| Unattributed gap | Unknown | Not set by anyone the buyer can name | Only by matching buyer spend to publisher revenue row by row |
What have industry studies found about fees?
A detailed public waterfall comes from ISBA's May 2020 study, run by PwC with the Association of Online Publishers. It covered 15 advertisers, 12 agencies, five DSPs, six SSPs and 12 publishers in the UK. Of 267 million impressions, 31 million, or 12 percent, could be matched end to end; the figures below describe those matched impressions.
| Step | Share of advertiser spend | Study note |
|---|---|---|
| Agency fee | 7 percent | Several fee models converted to percentage equivalents |
| DSP fee | 8 percent | Actual fees and contracts both averaged about 8 percent |
| Demand side tech fees | 10 percent | Mainly ad serving, verification and data |
| Unknown delta | 15 percent | About one third of supply chain costs; could not be attributed |
| SSP fee | 8 percent | About 14 percent of publisher revenue, against about 12 percent in contracts |
| Supply side tech fees | 1 percent | Exchange bidding fees of 5 percent of publisher revenue |
| Publisher revenue | 51 percent | Ranged from 49 to 67 percent by publisher |
ISBA's follow up study, summarized in January 2023 (opens in a new tab), reported that the unattributable spend, "AKA the unknown delta," fell to 3 percent from 15 percent, and that the share of advertiser spend reaching publishers "has risen by 8%." ISBA cautions that its results should not be taken as representative of the broader market.
US studies frame the gap more broadly than fees. The ANA's December 2023 study of the log level data of 21 major advertisers found that "Only 36 cents of every dollar that enters a demand-side platform (DSP) effectively reaches the consumer," per its programmatic transparency hub (opens in a new tab); that figure measures what reaches the consumer, a wider measure than intermediary fees. Its latest public benchmark, the Q1 2026 release (opens in a new tab) of May 27, 2026, found that "Transaction costs differed by just 2.4 percentage points between cohorts," while media productivity losses differed by 19.4 points. Both describe benchmark participants, not the whole market.
Can a seller file match tell me an SSP's take rate?
No. A take rate is the share of the clearing price an exchange keeps, which requires two amounts: what the buyer paid and what the seller received. The public supply chain records hold neither payout. The sellers.json specification (opens in a new tab) describes who is paid under each seller_id and whether that party owns the inventory, and the SupplyChain object (opens in a new tab) lists "all entities who are involved in the direct flow of payment." Its hp flag says a node takes part in payment; it carries no amount.
| Record | What it holds | What it cannot show |
|---|---|---|
| ads.txt | Which seller accounts the publisher authorizes, direct or reseller | Any fee or revenue share |
| sellers.json | The legal entity behind each seller_id and its seller_type | What that entity keeps or pays out |
| SupplyChain object | Each node in the payment flow, in order, with hp = 1 | The amount each node retains |
| Win notice price | OpenRTB 2.6 ${AUCTION_PRICE}, the clearing price "after discount" | The publisher's payout from that price |
| SSP revenue logs | Gross and net revenue per impression, when shared | Nothing about buy side fees |
A file match still matters for fees in one indirect way: it shows how many hops a path has. Each reseller node is another party paid from the same clearing price, so a long chain is a reason to ask for the amounts. The programmatic supply chain page maps who sits in each hop, and log level data explains how buyer and seller rows are joined.
How can buyers get fee transparency?
Five ways to see the fee layers
- Read your own contracts first. List the agency fee model, the DSP rate and each data or verification rate, with the basis each is charged on.
- Check the platform's fee settings. In DV360 the platform fee rate sits under Partner settings, and partner cost markups appear in reporting; confirm both match the agreements.
- Ask for sell side data with permission. ISBA's free audit toolkit (opens in a new tab) includes an Audit Permission Letter for gathering supply chain permissions, a data fields list and data principles.
- Match spend to publisher revenue. Join DSP impression rows to SSP rows on a shared auction ID; the unmatched remainder is the gap no contract explains.
- Prefer paths with fewer paid hops. Where a site sells directly on an exchange you buy through, compare that path's net to the publisher with the reseller path.
Standards bodies are working on the auction itself. On January 29, 2026 the Media Rating Council issued final Digital Advertising Auction Transparency Standards (opens in a new tab), covering disclosure and reporting for digital ad auctions across display, text, video and audio formats in digital, search, social, retail media, streaming CTV and addressable TV. The MRC says it supplements, not replaces, protocols such as OpenRTB.
Questions to put to each party about fees
- Agency: which fee model applies, and is any markup recorded as a partner cost?
- DSP: what is the platform fee rate, and which add on fees applied this month?
- Exchange: will it share revenue per impression for our deal under a permission letter?
- Resellers: which paid hops sit between the exchange and the publisher on this path?
- Publisher: what did it receive for our deal ID over the same dates?
What does a fee review look like on a real plan?
Fictional example
A dry cleaning and laundry pickup service in Oklahoma and Arkansas
An unnamed dry cleaning and laundry pickup service in Oklahoma City, Tulsa and Little Rock bought display on local news, careers and home and family sites through its agency. Its owner asked what share of the budget reached the publishers.
The agency built the answer in layers instead of quoting one figure. It listed its own fee and the DSP rate from the contracts, pulled the fee columns from platform reports, then asked the curated deal's exchange and two of the largest publishers on the list for revenue rows covering the same dates. Where no seller data came back, the review marked that layer unknown rather than estimating it. No performance figures are implied.
What can PlacementGraph show about selling paths before a fee review?
Frequently asked questions
Is the ad tech tax higher on the open exchange than in private deals?
In ISBA's 2020 UK study, private marketplace spend sent a larger share to publishers, 54 percent, than open marketplace spend, 49 percent, among impressions it could identify by marketplace. That is one historical UK sample, so treat it as a question to test with your own data, not a rule.
Does the ad tech tax include bid shading?
It can show up inside it. ISBA listed post auction bid shading among the possible explanations for its unknown delta, alongside fees missing from the data, financing arrangements, currency conversion and reselling between vendors. The study said it could not say with certainty what the delta represents.
Who pays the SSP fee, the buyer or the publisher?
The SSP's share comes out of the sale before the publisher is paid, so it does not appear as a line on the buyer's invoice. ISBA's 2020 study measured SSP fees as about 14 percent of publisher revenue in the data, against about 12 percent in contracts.
Can an advertiser cut fees by buying through fewer exchanges?
Fewer paths can reduce duplicate bidding and paid hops, but the saving depends on each path's terms. Compare the net amount reaching the publisher on each route, using matched data where possible, before consolidating spend.
Sources
- ISBA programmatic supply chain transparency study, executive summary (May 2020) (opens in a new tab)ISBA, in association with the AOP, carried out by PwC
- Programmatic supply chain study summary (January 18, 2023) (opens in a new tab)ISBA
- Financial audit toolkit for programmatic advertising (opens in a new tab)ISBA and the Cross-industry Programmatic Taskforce
- Programmatic Media Supply Chain Transparency (opens in a new tab)ANA
- ANA Programmatic Transparency Benchmark Reveals Widening Gap Between Top and Bottom Advertisers (May 27, 2026) (opens in a new tab)ANA
- Fees and billable cost (opens in a new tab)Google, Display & Video 360 Help
- sellers.json specification (opens in a new tab)IAB Tech Lab
- OpenRTB SupplyChain object (opens in a new tab)IAB Tech Lab
- OpenRTB 2.6 specification (opens in a new tab)IAB Tech Lab
- Digital Advertising Auction Transparency Standards (final, January 2026) (opens in a new tab)Media Rating Council
Researched and written by PlacementGraph Research. Read how we research, source and update these pages. Corrections: diana@placementgraph.com.