Could Google have introduced modelling for Upload / Offline Conversions in Google Ads?

[Mat]

Hi everyone,

We have been experiencing an unusual discrepancy in our Google Ads accounts over the past two weeks. Specifically: the number of Conversions shown in Google Ads is significantly higher than what we actually uploaded via the Upload / Offline Conversions feature (with valid GCLIDs etc.). Until recently, the upload numbers were always equal to or higher than what the Ads reporting showed (accounting for rejected uploads, “expired_event”, etc.).

We are aware that Google uses modelling (conversion estimation) in scenarios like Consent Mode for pixel/tag-based conversions when cookies are declined. However, to our knowledge, modelling has never been applied to Upload / Offline Conversions in this way: i.e. Google inventing (estimating) Conversions beyond what was uploaded, to compensate for lost data under cookie/privacy restrictions.

Has anyone else observed this behavior recently? Specifically:

• Do you see Ads reporting more Conversions than the number you uploaded?

• Has this changed in the last few weeks for your accounts?

• Have you found any official statements or documentation indicating that Google now applies modelling to Upload / Offline Conversions?

Any insights, screenshots, or diagnostic findings would be extremely helpful. Thanks in advance for your help!

[Mat]

For reference, I am referring to this Google Ads API feature:
https://developers.google.com/google-ads/api/samples/upload-offline-conversion

[Google Ads API Forum Advisor]

Hi,

Thank you for reaching out to the Google Ads API support team.

Based on the provided information, I understand that you are getting a discrepancy in conversion. Could you kindly confirm if you followed the setup prerequisites for working with an offline conversion setup? If not, I would request you to follow the prerequisites before uploading offline click conversions. I would suggest you refer to the Monitor offline data diagnostics documentation, as it helps to find the overall health of the conversion upload processes. 

The EXPIRED_EVENT error, which means that when uploading conversions, the click associated with the given identifier or ios url parameter is either too old to be imported or occurred outside of the click-through lookback window for the specified conversion action. For this error, you may double-check if the given identifier is not too old or occurred before the lookback window for the specified combination of conversion date and conversion action. You may use the click_view report resource to verify your GCLID. In addition, you can first verify the click_through_lookback_window_days specified in your conversion_action. From the value retrieved, then perform a request using the click_view report for each day (with date filter for one day) until the last valid date, in reference to the lookback window days. 

You can set the conversion window anywhere from 1 to 90 days, depending on the source of conversions. You can refer to this help center article About conversion windows for complete information.

In order to assist you further, kindly share the complete API logs (request and response logs with request-id and request header) generated at your end while uploading the conversions via the Google Ads API.

If you are using a client library and haven't enabled the logging yet, I would request you to enable logging for the specific client library that you are using. You can refer to the guides Java, .Net, PHP, Python, Ruby or Perl to enable logging at your end. For REST interface requests, you can enable logging via the curl command by using the -i flag.

You can send the details via Reply privately to the author option, or direct private reply to this email.

Thanks,
 

Google Ads API Team

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[2025-09-15 16:28:50Z GMT] This message is in relation to case "ref:!00D1U01174p.!500Ht01u6d8g:ref" (ADR-00332795)

[Mat]

Thank you for your answer that unfortunately didn't help. Let me rephrase my question for you:

Since early September 2025 we are seeing a discrepancy in Google Ads reporting: under the same conversion action, the account shows significantly more conversions and higher conversion value than we actually uploaded via Upload Offline Conversions using this workflow:
https://developers.google.com/google-ads/api/samples/upload-offline-conversion

All uploaded conversions include a unique order_id. Until August 2025, the reported numbers never exceeded our uploads (they were equal or sometimes slightly lower due to “expired_event” rejections).

Could you clarify why reporting now shows more conversions than were uploaded? Has modelling or another change recently been introduced for Offline Conversion Uploads?

[Google Ads API Forum Advisor]

Hi,

As per provided information, I understand that your Google Ads is reporting more conversions than you uploaded through the Google Ads API. Note that the discrepancy in the Google Ads may be due to a drop in the number of conversions that were uploaded successfully via the API. Also, the count of "successfully uploaded conversions" via the API doesn't necessarily equal the count of reported conversions, and this is expected. It is important to make sure that you are comparing the "successfully uploaded conversions" in both the API and the UI.I would recommend you refer to this Help Center article ​for more information regarding the discrepancies in conversion uploads. Please be informed that the uploaded conversions are reflected in reports for the "impression" date of the original click, not the date of the upload request or the date of the conversion_date_time of the ClickConversion.

Also, to report on conversions by conversion date in Google Ads, add the relevant 'by conv. time' columns, such as 'Conversions (by conv. time)' and 'Conv. value (by conv. time)' in Google Ads and compare the successful API uploaded data. 

In order to assist you further, could you please provide the Google Ads customer ID, conversion action name or ID and the date range for which you are facing discrepancy and also confirm how many conversions you have successfully uploaded through the Google Ads API? Also, provide the complete API logs (request and response with request-id and request header) generated at your end.

If you are using a client library and haven't enabled the logging yet, I would request you to enable logging for the specific client library that you are using. You can refer to the guides Java, .Net, PHP, Python, Ruby or Perl to enable logging at your end. For REST interface requests, you can enable logging via the curl command by using the -i flag.

You can send the details via Reply privately to the author option, or direct private reply to this email.

Thanks,
 

Google Ads API Team

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How was our support today?

               

[2025-09-16 10:54:49Z GMT] This message is in relation to case "ref:!00D1U01174p.!500Ht01u6d8g:ref" (ADR-00332795)