Google Ads conversion tracking: set it up and audit it

How Google Ads conversion tracking works

You need two pieces. In your account you create a conversion action such as "Purchase". On your site a tag sends a signal each time a customer checks out, with order value, currency and order number.

Every conversion action is either primary or secondary. Per Google Ads Help, primary actions show up in the Conversions column and drive bidding. Secondary actions appear only under All conversions, for observation. That single setting decides what Smart Bidding spends your budget on.

Google tag, GA4 import or store app

You can send the purchase signal three ways. Pick one as the primary source for purchases and keep the others secondary.

Per Google Ads Help, conversion actions you create from the Google Analytics interface start out as secondary. If you switch one to primary later, check first that the Google tag isn't already counting the same purchase.

Make purchase your only primary action

Your store makes money on orders, so Google should bid on orders. If "Add to cart" is primary, Google Ads counts every cart like a sale and buys you cheap cart clicks. The same logic applies to Smart Bidding, a target ROAS strategy and Google Ads AI Max: all of them learn from the actions you mark as primary.

Google recommends counting "Every" conversion for sales, because each purchase brings in revenue. "One" fits leads, where you only care whether a signup happened.

What we find in audits

In the Harucon analysis of 41 audits (audits from recent years through 2026), at least 19 of 41 accounts ran multiple primary conversion goals or misconfigured tracking. Three examples from those audits:

• In 2 accounts, "Add to cart" was the primary goal instead of purchase.
• One account had 76 active conversion actions, with page views set as primary.
• One account carried over 130 conversion actions, at least 6 of them parallel purchase actions.

A snapshot of 38 Google Ads accounts in the Harucon MCC, managed or under audit, from May to mid-August 2026 (n = 38), shows how common long lists of primary actions are:

Check campaign settings too. Google Ads Help states that a custom goal uses every conversion action it contains for bidding, whether that action is marked primary or secondary.

Conversion value: leave out shipping and tax

Many stores pass the full order total to Google Ads, product value plus shipping, sometimes plus sales tax. Google Ads only requires the value as a number and the currency as an ISO code. What goes into the value is your call. We recommend the product value before shipping and tax, because that's the number your contribution margin is built on.

Take a store with 1,000 orders a month at $100 product value, $10 shipping per order and $25,000 in ad spend:

If your checkout also passes sales tax, the gap grows further. The difference hits your bids. Say your break-even is a ROAS of 3.0 on product revenue after returns, and you enter a 300% target ROAS against the order total. Google hits the target, and your real ROAS lands at 2.18. How ROAS, break-even and POAS fit together is covered in ROAS meaning.

You can report returns after the fact. Conversion adjustments let you retract a conversion or restate its value. According to Google Ads Help, automated bidding reads adjustments made within 7 days of the original conversion, and you can adjust for up to 54 days.

Stop double counting

Double-counted purchases inflate ROAS and conversion counts. Smart Bidding then thinks a campaign is more profitable than it is and bids higher. The usual sources:

• Google tag and GA4 import both primary. One purchase counts twice. Keep one source primary.
• Store app plus an old hand-coded tag. Two purchase actions fire. Remove the old code.
• Customer reloads the thank-you page. The tag fires again. Pass a transaction ID.
• Leftover purchase actions from past setups. Each one counts the same order. Remove them.

The transaction ID is your main safeguard. Google Ads Help says a second conversion for the same action with the same ID gets flagged as a duplicate. The ID must be unique per order. A static ID for all orders causes Google Ads to heavily undercount conversions.

Enhanced conversions

Enhanced conversions add first-party customer data from the order to the tag: email address, name, home address or phone number. The data is hashed with the one-way SHA256 algorithm before it leaves the page. Google matches the hashes to signed-in Google accounts and attributes purchases the cookie alone would miss.

Online stores use enhanced conversions for web, which works with the data your customer already types into checkout. The enhanced conversions diagnostics report in Google Ads shows whether the data arrives.

Consent mode and server-side tagging

Consent mode passes the choice from your cookie banner to Google tags through four parameters: ad_storage, analytics_storage, ad_user_data and ad_personalization. In basic mode, tags wait until a visitor consents. In advanced mode, tags load right away with a denied default and send cookieless pings when a visitor declines. Google uses those pings to model the missing conversions, with a model fitted to your account in advanced mode.

Server-side tagging splits the setup into two containers. The web container in your store sends one request per event to a server container in a cloud environment, which forwards the data to Google Ads and other destinations. Tag Manager Help lists a lighter browser load and the option to strip personal data and validate values before they reach ad partners. Set it up once purchase action, value and transaction ID already work, since a wrong value stays wrong on a server.

Audit your conversion tracking in 7 steps

You can run this checklist yourself. You need access to Google Ads and to the order list in your store.

1. 01

   Open the conversions summary

   Under Goals you see every conversion action with its status, source and primary or secondary setting.

2. 02

   Cut primary actions to one

   Keep purchase primary. Set cart, checkout and signups to secondary, remove page views.

3. 03

   Check campaign goals

   If a campaign uses a custom goal, every action in that goal counts for bidding.

4. 04

   Check counting and value

   Purchase on "Every", value pulled dynamically from the order, before shipping and tax.

5. 05

   Test the transaction ID

   Place a test order and confirm in Tag Assistant that value, currency and order number arrive.

6. 06

   Read the diagnostics

   Status and tag diagnostics in Google Ads show whether actions record data and whether enhanced conversions come through.

7. 07

   Reconcile with your store backend

   Once a month, put purchases and value from Google Ads next to the orders in your store.

Expect some gap. Google Ads credits a purchase up to 30 days after the click by default, and consent mode adds modeled conversions. Large gaps usually trace back to one of these causes:

A good agency for Google Ads starts with this reconciliation before touching bids. We measure our own $100k guarantee on revenue in your store backend as well.