Google Analytics Audit Test #

49

Duplicate Transaction Ids

Why It Matters:

Critical to understanding user/site behavior and ROI/ROAS.

Industries:

Ecommerce

Checks For:

Accuracy

How accurate is your recent data?

Insight Category:

Behavior

Can you tell what visitors are doing?

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Background

A GA4 audit is essential for uncovering missing insights—key data points that organizations don't yet know and can act upon. A well-done audit evaluates both behavioral tracking and traffic attribution, ensuring each is accurate and useful. It also assesses whether the data collected truly supports business decisions and reporting.

Test Detail

This test identifies whether the same transaction_id is submitted more than once in GA4. Duplicate Transaction IDs can lead to:

  • double-counting revenue,
  • inflating conversion metrics,
  • and corrupting financial reports

especially in BigQuery or ecommerce dashboards.

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How to Conduct This Test

Basic Tests

  • Go to GA4 > Explore and build a free-form exploration.
    • Set dimension: Transaction ID
    • Set metrics: Transactions, Purchase Revenue
    • Sort by Transaction ID and look for IDs that appear more than once with non-zero values.

Advanced QA

  • Run the below query in BigQuery:
    SELECT transaction_id, COUNT(*) as count
    FROM `your_project.analytics_xxxxxxx.events_*`
    WHERE event_name = 'purchase'
    GROUP BY transaction_id
    HAVING count > 1
    ORDER BY count DESC;
  • If you’re seeing duplicates for the same ID, it’s likely due to tags firing more than once or confirmation pages being reloaded.

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How To Fix

  • In GTM or your site code, make sure the purchase event with transaction_id only fires once.
  • Add checks to avoid resending the same purchase event on reload or refresh.
  • If using server-side tagging, validate that server logic does not double-send conversions.
  • Consider storing transaction_ids in a session or cookie and blocking duplicates.
  • Hire a pro to fully debug and implement deduplication logic so your revenue stays accurate.

Tips from a Google Analytics Consultant

Focus on Insights

Every Google Analytics audit should result in a plan for more insights.

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An insight is:

  • something you don't know
  • and can act on to improve performance

The Goal

Identify and remove insight blockers. Don't get tempted to track things you can't act on!

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