What is the ad tech tax?
The ad tech tax is the share of an advertiser's budget taken by intermediaries, such as DSPs, SSPs, exchanges, data providers and verification vendors, before the money reaches the publisher. Studies differ, but the UK's ISBA and PwC found in 2020 that publishers received only about 51% of advertiser spend, with around 15% unaccounted for.
The ad tech tax is not a single fee but a stack: the DSP fee, data costs, the SSP or exchange take rate, sometimes agency trading desk margins and media rebates. The ISBA/PwC programmatic supply chain study traced individual impressions and could not match about 15% of spend to either side, the so-called unknown delta.
In the US, the ANA's programmatic transparency work has also estimated large inefficiencies; its Q2 2025 benchmark put wasted programmatic spend at $26.8 billion globally. Buyers reduce the tax through supply path optimization, direct publisher connections and contracts that require log-level fee transparency.