Does Amazon Consent Signal Affect ROAS? What UK and EEA Advertisers Need to Know
If you run Amazon Ads campaigns targeting users in the UK or European Economic Area, there's a good chance your ROAS reports are not showing your true performance. The cause is the Amazon Consent Signal — a requirement that has been in place since February 2025 and reaches full enforcement on June 30, 2026.
This post explains what the consent signal is, why it matters for ROAS, and what you need to do before the deadline.
What Is the Amazon Consent Signal?
The Amazon Consent Signal (ACS) is a set of data parameters that tells Amazon's advertising systems whether a specific user has agreed to data processing for advertising purposes. It must be passed alongside any personal data sent to Amazon Ads.
The signal includes two parameters: one for consent to store or access information on a user's device, and one for consent to use their personal data for advertising. Both must be present and valid. If either is missing or denied, Amazon treats all data associated with that user as non-consented — regardless of what your internal systems record.
How It Connects to ROAS
When a user has not given consent, Amazon cannot attribute their purchase to your campaign. The conversion still happens in the real world, but Amazon's system cannot record it. That unattributed conversion disappears from your ROAS calculation.
Your spend stays the same. Your recorded conversions go down. Your ROAS looks worse than it actually is.
There's also a targeting impact. Users who have not consented are removed from Amazon's retargeting and lookalike audience pools. This reduces the size and accuracy of the audiences your campaigns can reach.
Amazon Marketing Cloud (AMC) is also affected — reports on conversion paths, audience overlap, and campaign attribution lose accuracy when first-party data is incomplete.
Two Separate ROAS Issues
What You Need to Implement a Valid Consent Signal
Amazon requires advertisers to use a certified Consent Management Platform (CMP) to transmit the consent signal. An uncertified CMP, or one that passes incorrect parameters, may result in Amazon rejecting the signal entirely.
Seers AI is an Amazon-certified CMP. It integrates directly with Amazon Ad Tag, Conversions API, and Events API — collecting user consent, storing those preferences, and transmitting both required consent parameters accurately. Seers plans start free, with paid options from £8 per month covering up to 100,000 consent logs per domain.
The June 30, 2026 Deadline
Amazon's enforcement deadline for the Amazon Ad Tag, Conversions API, and Events API is June 30, 2026. After this date, advertisers without a valid consent implementation risk having their data processing restricted by Amazon's systems. The practical consequences include:
- Reduced audience targeting capability
- Incomplete attribution and conversion tracking
- Inaccurate ROAS reporting in Ads Console and Amazon Marketing Cloud
- Weaker machine learning signals affecting automated bidding
The earlier you implement, the less compounding data loss you face. For the full technical breakdown of how consent affects each part of your Amazon Ads setup, read the complete guide here.
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