In one project:
• the gateway records more transactions than GA4;
• purchase events don’t pass fully through GTM and API to GA4 reporting.
I’ve seen cases where some purchases stay outside GA4 due to transfer errors, ID mismatches, and incomplete handoffs in the GTM chain — results are discrepancies and skepticism about the numbers.
What problems arise from differences between GA4 and the gateway?
Differences lead to incorrect attribution: some sales appear only on the gateway side and don’t show up as purchases in GA4.
This destabilizes ROI and budgets: decisions are made on an incomplete picture that doesn’t match real demand.
The takeaway - align the identifiers
The main data loss happens during transfer through GTM and API; you need to map the gateway, GTM and GA4, check unique identifiers and mapping correctness.
Without a single identity standard, data splits by channel and device and the overall view becomes distorted.
What to do next:
• Validate the flow of e-commerce events from gateway through GTM to GA4; ensure presence of IDs like transaction_id and other key markers.
• Run a pilot on one channel, compare results in BigQuery, fix duplicates and gaps, document the methodology for the whole team.
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