Question from Reddit user:
Hi everyone,
I want to build my own offline conversion automation, but for it to be accurate, I need to know the GCLIDs that are coming from the “Calls from ads” calls. Where can I find those?
Thanks
Answer from Nabil:
The short answer is:
Achieving 100% lead tracking is challenging due to cross-device and third-party platform limitations, but you can get extremely close and significantly improve your ROAS accuracy by moving your tracking and attribution logic server-side.
The key is to use the Google Ads API to upload Offline Conversions and implement cross-domain tracking for your third-party booking site.
This process connects the initial Google Ads click ID (gclid) to the final, high-value conversion event, whether it’s an offline call, a form-to-sale conversion, or a booking on a third-party CRM, effectively bridging the data gaps your Google representative mentioned.
The long answer is:
Your Google representative and tag tech are technically correct about the limitations of standard client-side tracking, but those limitations can be overcome with a modern, server-side data infrastructure.
Your goal to track all high-value leads and calculate a true ROAS is achievable by connecting your business’s definitive conversion points—your CRM/backend system—directly to Google Ads.
For the cross-device call scenario, where a user sees an ad on a desktop and calls from a separate phone, this is impossible to track client-side.
The solution is to use Google Ads Call Tracking.
If you use Google’s own call forwarding numbers on your site or in your extensions, Google can log the gclid for the original ad click and connect it to the ensuing phone call on their server.
You can then use the Google Ads API to fetch the details of these calls, allowing you to match a specific call to a lead in your CRM.
If you use a third-party call tracking provider like CallRail, they capture the gclid using their own scripts and you can use the CallRail API to extract the gclid and conversion data directly from their platform.
For the online booking on a third-party CRM and the quote form submissions that lead to sales, the solution requires two steps: First, to track the third-party booking, you must set up cross-domain linking in Google Tag Manager.
This passes the Google Ads click ID (gclid) from your primary website to the third-party booking CRM’s URL.
Even if you can’t install a conversion tag on the CRM, the CRM’s backend must be configured to capture and store the gclid when the booking occurs.
Second, and this applies to both the booking and the quote form leads that result in a sale, once the high-value conversion (the actual booking or sale) happens in your backend system, you use the Google Ads API to upload that conversion data as an Offline Conversion.
This is the only way to accurately track the full sales cycle.
Your backend system holds the truth (booked lead, revenue amount, and the original gclid), and the Google Ads API allows you to send that truth directly back to Google Ads, telling it exactly which ad and click led to the revenue.
For call attribution, to distinguish between an organic Google My Business call, an organic website call, and a Google Ads call, you must use Dynamic Number Insertion (DNI) via a call tracking provider, which displays a unique phone number based on the traffic source.
This entire process is best managed using a server-side solution like Stape or Google Cloud Platform to process the data, perform the necessary matching, and call the respective APIs, ensuring the most accurate and complete attribution for true ROAS calculation.
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