What You Will Learn
- Why conversion tracking is the foundation of any Smart Bidding strategy
- Tag-based conversion tracking setup using the Google tag
- Importing GA4 conversions into Google Ads
- Call conversion tracking for phone-based businesses
- Enhanced Conversions — improving accuracy with hashed first-party data
- Setting conversion values for revenue-weighted bidding
- How attribution models distribute conversion credit across touchpoints
Why Conversion Tracking Matters
Conversion tracking is the single most important technical setup in a Google Ads account. Smart Bidding strategies (Target CPA, Target ROAS, Maximise Conversions) use conversion data as their primary input — without accurate conversion data, the algorithm optimises in the dark. An account running Smart Bidding without verified conversion tracking will either not spend (if no conversions are recorded) or optimise toward incorrect signals.
Beyond Smart Bidding, conversion tracking is the only way to measure campaign ROI. Click and impression data is available without tracking, but whether those clicks produce business value — purchases, leads, sign-ups, calls — is invisible without conversion tracking correctly implemented.
The Google Tag Assistant Chrome extension verifies that your conversion tag fires correctly. Test every conversion action before spending budget — a misconfigured tag that fires on the wrong page or fails to fire at all produces bad data that corrupts Smart Bidding and all performance reporting.
Tag-Based Conversion Tracking
Tag-based conversion tracking places a Google conversion tag (a JavaScript snippet from the Google Ads interface) on the page a user reaches after completing a conversion — typically a "Thank You" or order confirmation page. When a user who clicked a Google ad reaches this page, the tag fires and records a conversion.
Setup process
- In Google Ads: Goals → Conversions → New Conversion Action → Website
- Configure conversion settings: name, category (Purchase, Lead, Sign-up), value (fixed or dynamic), count (every conversion or one per click), conversion window (how many days after click to count), view-through conversion window
- Get the tag: Google generates a global site tag (Google tag) and an event snippet specific to this conversion
- Install the Google tag on every page of your site (once, in the
<head>) - Install the event snippet only on the conversion confirmation page
- Verify with Google Tag Assistant that the tag fires correctly on the confirmation page
Dynamic conversion values for e-commerce
For e-commerce, pass the actual transaction value to the conversion tag rather than a fixed value. This enables Target ROAS bidding and accurate ROAS reporting. Configure the event snippet to include the dynamic value variable:
gtag('event', 'conversion', {
'send_to': 'AW-CONVERSION_ID/CONVERSION_LABEL',
'value': transaction_value, // actual order total
'currency': 'GBP',
'transaction_id': order_id // prevents duplicate counting
});GA4 Conversion Import
If GA4 is already tracking conversions on your site, you can import those conversions directly into Google Ads rather than implementing a separate Google Ads tag. This approach uses GA4 as the single source of conversion truth — avoiding discrepancies between GA4 and Google Ads conversion counts.
Setup process
- Link your GA4 property to Google Ads: in Google Ads, Tools → Linked Accounts → Google Analytics → link your property
- In Google Ads: Goals → Conversions → new conversion action → Import → Google Analytics 4 Properties
- Select the GA4 conversion events to import
- Set conversion window, value settings, and Smart Bidding eligibility
Imported GA4 conversions use GA4's last-click attribution by default — this can differ from Google Ads' data-driven attribution. For Smart Bidding, ensure the imported conversion uses Google Ads data-driven attribution for optimal signal quality.
Call Conversion Tracking
Call conversions track phone calls generated by Google Ads. Three methods:
- Calls from ads (call extensions). Tracks calls made directly from the call extension in the ad — using a Google forwarding number. No website tag required. Set a minimum call duration to count as a conversion (e.g. calls over 60 seconds indicate genuine interest).
- Calls to a number on your website. A dynamic number insertion tag on your website replaces your phone number with a Google forwarding number for users who arrived via a Google ad. Tracks calls from users who clicked through to the website.
- App call conversions. For mobile apps, tracks calls made from in-app call buttons.
Enhanced Conversions
Enhanced Conversions improve conversion measurement accuracy in a cookie-restricted environment (iOS privacy changes, browser cookie blocking) by sending hashed first-party customer data (email addresses, phone numbers, names) alongside the conversion tag. Google uses this hashed data to match conversions to ad interactions that cookies may have missed.
Enhanced Conversions for Web: the conversion tag sends hashed customer data (from form completion, checkout) — Google matches it to signed-in Google accounts, recovering conversions that cookie restrictions would have lost. Implementation requires minor tag modification or the Enhanced Conversions setting in Google Tag Manager.
Enhanced Conversions for Leads: for lead generation businesses where the actual conversion (sale) happens offline or after a delay, you can upload the hashed email from form completions and later match them to actual sales from your CRM — providing Google's algorithm with the signal of what a quality lead looks like.
Conversion Values and Value Rules
Conversion values tell Google's bidding algorithm what each conversion is worth — the foundation for Target ROAS bidding. Three approaches:
- Fixed value. Every conversion counts as the same value (e.g. every lead is worth £50). Simple but ignores actual variation in conversion quality.
- Dynamic value (e-commerce). The actual transaction value is passed to the conversion tag. Ideal — Smart Bidding uses real revenue to calculate ROAS.
- Conversion Value Rules. Modify the reported conversion value based on specific conditions — device, location, audience. Example: conversions from mobile users are worth 20% less (set a 0.8 multiplier for mobile); conversions from London users are worth 30% more (set a 1.3 multiplier for London targeting).
Attribution Models
Attribution models determine how conversion credit is distributed across the Google Ads touchpoints (clicks and impressions) that occurred before a conversion. The choice of attribution model affects what Smart Bidding optimises toward and how performance appears across campaigns.
| Model | Credit Distribution | Best For |
|---|---|---|
| Last Click | 100% to the last click before conversion | Simple; favours bottom-funnel keywords |
| First Click | 100% to the first click in the journey | Evaluating awareness campaign contribution |
| Linear | Equal credit to all touchpoints | Values all touchpoints equally |
| Time Decay | More credit to clicks closer to conversion | Considers recency without ignoring earlier touchpoints |
| Position Based | 40% first + 40% last + 20% middle | Values both discovery and closing touchpoints |
| Data-Driven | AI-assigned based on actual conversion path data | Recommended — uses your account's actual data to determine contribution |
Data-Driven Attribution is Google's recommended model and the default for accounts with sufficient conversion volume. It uses machine learning to assess which touchpoints genuinely contributed to conversions based on the paths of converting vs non-converting users in your account. Smart Bidding performs best with Data-Driven Attribution because the signal more accurately reflects which keywords and ads drive conversions.
Authentic Sources
Official conversion tracking setup documentation.
Enhanced Conversions implementation for web and leads.
All attribution models and how Data-Driven Attribution works.