Why it happens
GA4 never got the purchase. An imported conversion can only be as complete as GA4. If the GA4 tag did not fire, because of an ad blocker, a declined cookie banner or a buyer who closed the page before it loaded, the sale is missing in GA4 and in Google Ads. GA4 shows fewer purchases than Shopify covers this first step.
GA4 could not tie the purchase to the Google ad. Google Ads counts an imported purchase only when it can link it to a Google Ads click. That needs auto-tagging on, the Google click ID kept on the landing page, and a purchase that GA4 joins to the visit that carried it. Google's help warns that the click ID must not be "altered or dropped by your website (for example, because of redirects)". A purchase that GA4 records as direct or unassigned stays in GA4 and never reaches Google Ads. See GA4 purchases show as direct or unassigned.
Google Ads only takes paid credit. For web conversions, GA4 lets you choose which channels can get credit when conversions are shared with Google Ads: Google paid channels, or paid and organic channels. A buyer who clicked your ad and then came back through organic search may get no Google Ads credit, depending on that choice and on your attribution model.
The windows are shorter. Google's help says Google Ads cookies expire 90 days after a click and a conversion window runs from 1 to 90 days, while Analytics uses a cookie that lasts up to 2 years. A purchase outside the conversion window is recorded in GA4 but not in Google Ads.
Google Ads dates the sale by the click. Google Ads reports a conversion on the date of the click that led to it. GA4 reports it on the day it happened. Last week in Google Ads can include sales that GA4 put in this week.
The data arrives late. Google says imported conversion data reaches Google Ads up to 24 hours after it happened. The last day of any report is always short.
No view-through, and no cross-device without signals. Google's help says imported conversions do not include view-through conversions, and cross-device conversions need Google signals on in GA4. A Google Ads action from its own tag can show both.
The action is Secondary. Google Ads sets actions based on GA4 key events to Secondary "to prevent counting the same event twice for bidding". A Secondary action is in All conversions but not in the Conversions column. If you look at Conversions, the imported purchase can seem to be missing entirely.
Check it yourself
- 1In GA4, check that purchase is marked as a key event; only key events can be imported. GA4 purchase as a key event shows the import steps.
- 2In GA4, open Admin > Product links > Google Ads links and check the link to the right Google Ads account. In Google Ads, check that auto-tagging is on.
- 3In GA4, compare the purchases for one full week with your Shopify paid online orders. If GA4 is already far below Shopify, start there.
- 4In GA4, open Reports > Acquisition > Traffic acquisition and look at purchases from google / cpc. That is roughly the most Google Ads can import.
- 5In GA4, check Advertising > Conversion management > Conversion attribution settings: paid channels only, or paid and organic.
- 6In Google Ads, open Goals > Conversions > Summary. Find the imported purchase, see whether it is Primary or Secondary, and read its conversion window.
- 7Compare whole weeks, use All conv. (by conv. time) in Google Ads, and leave out the last 24 hours.
- 8Click your own ad and look at the landing page address. It should keep the gclid parameter after any redirect.
FAQ
Is it normal for Google Ads to show fewer purchases than GA4?
Yes. GA4 counts purchases from every channel. Google Ads counts only those it can credit to its ads, inside its window, on the click date.
Should I use the GA4 import or a Google Ads purchase conversion?
Google Ads can measure purchases with its own conversion action, or import them from GA4. Its own action can include view-through conversions; the import keeps one definition across both tools. Use one as the Primary purchase action, not both, or each sale can count twice.
Why did the imported number drop after I changed a setting?
Changes to the attribution settings in GA4 apply from that day on, and Google Ads bidding needs time to learn again. Compare the weeks before and after the change, not single days.
Does consent mode change what Google Ads imports?
Yes. Google's help says that from 15 June 2026, consent mode in Google Ads is the single control for collecting Google Ads cookies and IDs through the Google Analytics tag. With fewer IDs, fewer purchases can be tied to an ad.
Will the numbers ever match Shopify?
No. Shopify counts each paid order. Google Ads counts the purchases it can tie to its own clicks.