Google Ads Conversion Tracking for E-commerce: Setup Guide

Google Ads conversion tracking for e-commerce means sending every completed purchase, with its order value, currency and transaction ID, back to Google Ads. The cleanest setup is a Google Ads purchase conversion fired from your order confirmation page, set as the only primary conversion, with enhanced conversions and Consent Mode v2 turned on. Everything else, such as add-to-carts and GA4 events, should be secondary so it does not distort bidding.

This guide walks through each piece in order, explains the choices you will face and shows how to check that the numbers are right.

Why tracking quality decides campaign performance

Google Ads bidding is only as good as the conversion data you give it. Smart Bidding strategies like Maximize Conversion Value and target ROAS use your conversion data to decide how much to bid on every auction.

If tracking is wrong, bidding goes wrong:

• Missing purchases make good campaigns look unprofitable, so bids drop.
• Double-counted purchases make campaigns look better than they are, so bids rise and you overspend.
• Missing values mean Google cannot tell a $20 order from a $400 order.
• Counting add-to-carts as conversions teaches Google to find people who add to cart, not people who buy.

Get tracking right before you judge or scale any campaign.

Step 1: Decide what counts as a conversion

For an e-commerce store, there is one conversion that matters most: a completed purchase. That should be your primary conversion.

Other actions can be useful to track, but as secondary conversions:

• Add to cart
• Begin checkout
• Newsletter signup
• Account creation

Primary vs secondary conversions

Every conversion action in Google Ads is either primary or secondary.

Google Ads groups conversion actions into goals, such as Purchase or Add to cart. Campaigns use your account-default goals unless you set campaign-specific goals. For most stores, the account-default goal should be Purchase, and nothing else should be primary.

You can change this under Goals, then Summary, by editing the conversion action and setting it to primary or secondary.

Step 2: Choose your tracking method

You have two main ways to get purchase data into Google Ads.

Option A: Google Ads conversion tag

A Google Ads conversion action fired directly from your site, using the Google tag or Google Tag Manager.

Pros:

• Data reaches Google Ads directly, usually faster.
• Uses Google Ads attribution and conversion windows.
• Supports enhanced conversions directly.
• Generally the recommended choice for bidding.

Cons:

• Separate from your analytics setup, so it needs its own maintenance.

Option B: Import GA4 purchases into Google Ads

Link GA4 and Google Ads, then import the GA4 purchase key event as a Google Ads conversion.

Pros:

• One measurement setup to maintain.
• Fine for simple stores already running GA4 well.

Cons:

• Imported conversions can arrive later than tag-based ones.
• GA4 and Google Ads can count and attribute differently.
• Any GA4 problem now affects your bidding too.

Which should you use?

For most e-commerce stores, use the Google Ads conversion tag as primary. Keep GA4 for analytics. If you also import the GA4 purchase, set it as secondary so you can compare numbers without double counting.

What about platform apps?

Shopify's Google & YouTube app and WooCommerce's Google integration can set up Google Ads purchase tracking for you. They are often the simplest route and handle values and transaction IDs automatically. The main risk is adding a manual tag on top of an app that already tracks purchases, which causes double counting. Platform-specific setup is covered in our guides on Google Ads for Shopify and Google Ads for WooCommerce.

Step 3: Create the purchase conversion action

In Google Ads:

1. Go to Goals, then Conversions, then Summary.
2. Click New conversion action and choose Website.
3. Enter your store's domain and choose to set up manually (or use the Google tag if you prefer).
4. Choose the Purchase category.
5. Set Value to "Use different values for each conversion." Enter a default value, which is only used if no value is sent.
6. Set Count to Every. Each purchase is a separate sale. "One" is for leads, not orders.
7. Set the click-through conversion window. 30 days is the default and suits most stores. Longer consideration products may justify longer.
8. Choose Data-driven attribution, the default for most accounts.
9. Save and note your conversion ID and conversion label. You will need them for GTM.

What value should you send?

Decide this once and stay consistent:

• Revenue including tax and shipping matches what the customer paid, but overstates what you earned.
• Revenue excluding tax and shipping is the most common choice and lines up better with product margins.
• Profit or margin-adjusted value is the most accurate for bidding, but requires more setup.

Whatever you send, your ROAS targets must use the same definition. If you send revenue excluding tax and shipping, calculate your break-even ROAS on that basis using the break-even ROAS calculator.

Step 4: Install the tag with Google Tag Manager

If your platform app does not handle tracking, Google Tag Manager (GTM) is the most flexible way to install it.

4.1 Make sure the data layer has purchase data

Your order confirmation page needs to push purchase details into the data layer. Many platforms and plugins do this using the standard GA4 e-commerce format:

• event: purchase
• ecommerce.transaction_id: a unique order number, such as 10452
• ecommerce.value: the order value, such as 84.00
• ecommerce.currency: a currency code, such as USD
• ecommerce.items: the products in the order

If your store does not push this, a developer or plugin needs to add it. Without it, you cannot send accurate values.

4.2 Create the variables

In GTM, create Data Layer Variables for:

• ecommerce.value
• ecommerce.currency
• ecommerce.transaction_id

4.3 Add the Conversion Linker tag

Create a Conversion Linker tag that fires on all pages. It stores ad click information so conversions can be attributed to the right click.

4.4 Add the Google Ads Conversion Tracking tag

1. Create a new tag of type Google Ads Conversion Tracking.
2. Enter your conversion ID and conversion label.
3. Map Conversion Value to the value variable.
4. Map Transaction ID to the transaction ID variable.
5. Map Currency Code to the currency variable.
6. Set the trigger to a Custom Event trigger for the purchase event.

4.5 Test before publishing

Use GTM Preview mode with Tag Assistant:

1. Place a test order, ideally with a discount code or a low-cost product you refund.
2. Confirm the conversion tag fires once on the confirmation page.
3. Confirm the value, currency and transaction ID are filled in correctly, not empty or "undefined."
4. Publish the container.

In Google Ads, the conversion action status should change from "Inactive" or "No recent conversions" to "Recording conversions" within a day or so after real orders come in.

Step 5: Turn on enhanced conversions

Enhanced conversions improve measurement by sending hashed first-party customer data, such as email address, phone number and name and address, along with the conversion. Google matches it to signed-in Google accounts to attribute conversions that cookies alone would miss.

The data is hashed with SHA-256 before it is sent, and Google provides the setup inside the tag.

How to set it up

1. In Google Ads, go to Goals, then Settings (or open your conversion settings), and turn on enhanced conversions for web. Accept the customer data terms if prompted.
2. Choose your method: Google tag, Google Tag Manager or the Google Ads API.
3. In GTM, open your Google Ads Conversion Tracking tag, check Include user-provided data from your website and create a User-Provided Data variable.
4. Map the variable to your data layer fields for email, phone and address. Automatic collection exists, but manual mapping from the data layer is more reliable.
5. Test with Tag Assistant to confirm user data is detected.
6. Check the Diagnostics tab on your conversion action after a few days.

Shopify and WooCommerce integrations often support enhanced conversions with a toggle. Check your app's settings before building it yourself.

Step 6: Set up Consent Mode v2

Consent Mode lets your Google tags adjust their behavior based on whether a visitor agreed to cookies. Version 2 uses four consent signals:

Who needs it

If you serve ads or measure visitors in the European Economic Area or the UK, Google requires Consent Mode v2 signals for its advertising and measurement features to work fully with those users. Without it, you can lose conversion measurement and remarketing audiences for that traffic. US-only stores are not under the same Google requirement, but several US states have their own privacy laws, so check what applies to you.

Basic vs advanced mode

• Basic: Google tags do not load until the visitor consents. No data is collected from people who decline.
• Advanced: tags load with consent defaulted to denied and send cookieless signals. Google uses these to model conversions from users who did not consent.

Advanced mode usually recovers more measurement, but you should choose based on your legal advice and privacy policy.

How to implement

1. Use a consent management platform (CMP) that supports Consent Mode v2. Google lists certified CMP partners.
2. Set default consent states before any Google tags fire.
3. Update consent states when the visitor makes a choice.
4. In GTM, use the CMP's template and check Consent Overview to confirm each tag's consent requirements.
5. Test with Tag Assistant, which shows consent state on each event.

Step 7: Avoid double counting

Double counting is one of the most common tracking problems in e-commerce accounts. Check for these causes:

• Two primary purchase actions. For example, a Google Ads tag and an imported GA4 purchase, both primary. Keep one primary, set the other secondary.
• App plus manual tag. A platform app tracks purchases and someone also added a GTM tag. Pick one.
• Confirmation page reloads. A customer refreshes the thank-you page or returns to it from an email. Sending a transaction ID lets Google Ads deduplicate repeats of the same order.
• Count set to "One" or "Every" incorrectly. Purchases should be "Every," but they still need transaction IDs to deduplicate.
• Multiple Google Ads accounts tracking the same store with cross-account conversion tracking misconfigured.

To spot problems, compare a week of Google Ads conversions (using the "Conversions by conversion time" column) against orders in your store platform that came from Google paid traffic. They will not match exactly, because attribution differs, but Google Ads should not report more purchases than you received in total.

Step 8: Handle refunds and cancellations

Google Ads records the purchase at checkout. If an order is refunded, the conversion stays unless you correct it.

For stores with meaningful return rates, use conversion adjustments to retract or restate conversions by transaction ID. You can upload them manually or automate them through the API. At minimum, factor your return rate into your ROAS targets.

A conversion tracking checklist

1. One primary conversion: Purchase.
2. Purchase action counts Every conversion.
3. Dynamic value sent on every purchase.
4. Currency sent on every purchase.
5. Transaction ID sent on every purchase.
6. Conversion Linker tag on all pages.
7. Enhanced conversions turned on and showing healthy in diagnostics.
8. Consent Mode v2 implemented with a supported CMP, if you serve EEA or UK users.
9. GA4 purchase import, if used, set to secondary.
10. No duplicate tags from apps and GTM.
11. Google Ads conversions checked against store orders.
12. A plan for refunds and returns.

When tracking is solid, everything else gets easier

Once tracking is accurate, you can trust your ROAS, set budgets with confidence and let Smart Bidding work. See our guides on what a good ROAS is and setting your Google Ads budget for the next steps.

If you would rather have someone else set this up and audit it, Mercantads handles conversion tracking as part of every account we manage, from tag setup and enhanced conversions to Consent Mode. Talk to us about your store.

Frequently asked questions

Should I use the Google Ads tag or import conversions from GA4?

For most e-commerce stores, the Google Ads conversion tag is the better primary conversion for bidding because it reports directly to Google Ads. You can still import the GA4 purchase as a secondary conversion for comparison.

Why does Google Ads show different numbers than my store?

Google Ads attributes conversions to the date of the ad click by default and only counts purchases it can connect to an ad interaction. Your store counts every order on the order date, so some difference is normal, but Google Ads should never show more purchases than you actually received.

Do I need enhanced conversions for ecommerce?

It is not required, but it is recommended. Enhanced conversions use hashed customer data to attribute purchases that cookies miss, which gives Smart Bidding more complete data.

Is Consent Mode v2 required for US stores?

Google's Consent Mode v2 requirement applies to traffic from the EEA and UK. A US-only store is not bound by that requirement, but it still needs to follow any US state privacy laws that apply to its visitors.

How do I stop Google Ads from double counting purchases?

Make sure only one purchase conversion action is primary, avoid running a platform app and a manual tag for the same purchase, and send a unique transaction ID with every order so Google Ads can deduplicate repeats.