Every ad platform reports its own ROAS. Google Ads says 4.2. Meta says 3.8. TikTok says 5.1. Summed, they claim to have generated more revenue than your store actually produced. That is not an accounting error. It is the platforms each taking credit for the same conversions.
Operators who believe platform-reported ROAS overspend. Operators who know the gap, adjust. Connecting Google Ads, Meta, TikTok, GA4, and Shopify to Claude through CorpusIQ gives you the blended view in minutes instead of building a Northbeam subscription around it.
Why platform ROAS is misleading
Three mechanisms inflate it.
View-through conversion. Meta counts a sale if the user saw an ad in the last 1-7 days, even if they did not click. If that user also clicked a Google ad, Google also counts it.
Attribution window generosity. Most platforms use a 7-day click and 1-day view window by default. Longer windows capture more conversions per dollar, making ROAS look better.
Self-reporting incentive. Every platform is incentivized to show high ROAS. They set defaults that are favorable to themselves.
The consequence: operators read three platform reports, think ads are working, spend more. The actual revenue does not grow as fast as the reported ROAS suggests it should.
The truth report
Two metrics cut through the attribution noise.
MER (Marketing Efficiency Ratio): total revenue divided by total ad spend, across all platforms. Does not rely on attribution at all. Treats the whole ad budget as one investment and measures whether revenue follows.
Incremental blended ROAS: total ad spend divided into total revenue from all paid sources per GA4. More precise than MER but depends on GA4 attribution, which has its own issues.
For most brands, MER is the cleanest weekly number. Track it over time. Trend matters more than absolute value.
The weekly truth report prompt
Pull the following for last week:
From Shopify: total revenue, order count, AOV, new customer count.
From Google Ads: total spend, platform-reported conversions and revenue.
From Meta Ads: total spend, platform-reported conversions and revenue.
From TikTok Ads: total spend, platform-reported conversions and revenue (if connected).
From GA4: paid traffic sessions, paid conversions, paid conversion revenue.
Calculate:
1. Total ad spend across all platforms
2. MER (Shopify revenue / total ad spend)
3. Platform-reported ROAS per channel (platform revenue / platform spend)
4. Sum of platform-reported revenue versus Shopify total revenue
5. GA4 paid conversion revenue versus sum of platform-reported
Highlight:
- The gap between summed platform ROAS and MER
- Any platform where platform-reported ROAS has diverged from GA4-attributed
ROAS over the last 4 weeks
- MER trend compared to the prior 4 weeks
Claude synthesizes across five connectors. Output is a clear truth report in five minutes instead of an afternoon of spreadsheet work.
What to do with the findings
Four actions flow from the truth report.
First, set an MER target. Most ecommerce brands target 3.0-5.0 depending on margin structure. Watch weekly. If MER compresses below target, the ad budget is not earning its keep.
Second, identify the platform with the biggest attribution inflation. If Google Ads claims $50k and GA4 shows $30k from paid search, Google's self-reporting is suspect. That does not mean stop spending on Google. It means discount the reported ROAS.
Third, run holdout tests. The only true way to know incremental ad impact is to pause a channel for a week and measure. Claude can quantify the revenue impact of the holdout by comparing to the prior period.
Fourth, reallocate. Channels with the most inflated attribution are often the ones to cut first when MER compresses. The non-incremental portion of their spend was waste.
How to set it up
- Sign up at corpusiq.io. Solo $29.95/month covers all the connectors needed.
- Connect Shopify, Google Ads, Facebook Marketing, TikTok (if applicable), and Google Workspace for GA4.
- Add CorpusIQ MCP to Claude.
What this does not replace
Two things.
Advanced attribution modeling. Tools like Northbeam, Triple Whale, and Wicked Reports build media mix models using statistical techniques. This workflow is directional, not rigorous. For brands over $50M ad spend, proper MMM is worth the investment.
Creative-level optimization. The truth report tells you whether the whole ad budget is working. It does not tell you which creative is working. Use the platform ad-level reports for that, with the caveat that attribution there is also self-reported.
The value of the truth report is not perfect accuracy. It is seeing the scale of the attribution inflation and treating platform ROAS as a signal, not gospel.
See also
FAQ
Why do ad platforms report different ROAS numbers?
Each platform takes credit for conversions that touched any of their ads in the attribution window. The same customer often gets counted by Google, Meta, and TikTok. Platform ROAS summed is always higher than actual ROAS.
What is MER and why does it matter?
Marketing Efficiency Ratio: total revenue divided by total ad spend. It ignores attribution entirely and measures whether the whole ad budget is working. For most ecommerce brands, MER is the cleanest north-star metric.
Does this replace Triple Whale or Northbeam?
Not directly. Those tools do advanced attribution modeling. This workflow is lighter: it blends platform data against Shopify and GA4 for a quick truth check, without another subscription.