AI Max's bidding model makes bid adjustments based on predicted conversion probability. This prediction is anchored to your attribution window setting — how many days after a click a conversion is counted. If your customers typically take 60 days from first click to purchase, but your attribution window is set to 30 days, the AI is missing half your conversions. Here's how to fix this.
What Attribution Windows Are
In Google Ads, an attribution window defines how long after a click or impression a conversion will be credited back to that click. Default windows:
- Click-through conversion window: 30 days (default)
- Engaged-view conversion window: 3 days (video)
- View-through conversion window: 1 day (Display)
These defaults work for e-commerce with short consideration cycles. They're wrong for:
- B2B software (30-90 day sales cycles)
- Automotive (90-180 day consideration cycles)
- Luxury goods (variable, often 30-90 days)
- Financial services (mortgage research can take months)
- Higher education (admission cycles span months to a year)
Why Wrong Windows Break AI Max Bidding
AI Max's model trains on the conversion data it can observe within your attribution window. If you have a 45-day consideration cycle but a 30-day window:
- User clicks AI Max ad on Day 1
- User converts on Day 40
- Conversion falls outside the 30-day window — NOT recorded to AI Max
- AI Max sees a conversion-less click → treats this query/user type as non-converting
- AI Max bids lower for this query type in the future
- You lose auctions you should be winning
Effect: AI Max appears to have lower ROAS than actual business ROAS because it's missing conversions that occur outside the window.
How to Adjust Attribution Windows for AI Max
In Google Ads: Tools > Conversions > [conversion action] > Edit settings > Attribution window
Maximum windows available:
- Click-through: up to 90 days
- Engaged-view: up to 30 days
- View-through: up to 30 days
For B2B and long-consideration products: set click-through window to 90 days if your sales cycle supports it. Longer windows mean:
- More conversions recorded
- Better AI training data
- More accurate bidding
- Delay in seeing conversion data (90-day lookback means this month's conversions don't fully appear for 90 days)
Modeled Conversions and Attribution Windows
When you use longer attribution windows, some conversions will be modeled (especially for Consent Mode v2 users in GDPR regions) because users may have denied cookies that would have tracked the full 90-day path. The modeled conversions supplement actual observed conversions.
The July 2026 ToS (https://yositeup.com/blog/google-ads-tos-july-2026-ai-automation-what-changed) maintains transparency requirements for how modeled conversions are reported. For AI Max advertisers: you can see in your Conversion report which conversions are "modeled" vs. "observed" if you segment by conversion type.
Attribution Window Choice by Business Type
E-commerce (standard): 30 days click-through — appropriate for most retail with short consideration
E-commerce (high-ticket, luxury): 60 days — covers extended research phase for items over $500
Lead generation to B2C sale: 30-60 days — depends on your sales team's close cycle
B2B software or services: 60-90 days — most appropriate for sales cycles involving procurement and approvals
Automotive: 90 days — standard for automotive industry; some manufacturers use even longer windows for reporting (though 90 is the GA max)
Insurance: 60-90 days — comparison shopping and underwriting delays
The June 2026 Deletion and Attribution Window Data
The June 2026 data deletion (https://yositeup.com/blog/google-ads-reporting-data-deleted-june-2026) affected conversions reported in the deleted period. For advertisers with long attribution windows (90 days), this means:
- A click that happened in March 2026 that converted in June 2026 — the conversion credit is in the deleted period
- AI Max lost training data for those high-value late conversions
- If you use 90-day windows for a long-consideration product, the data loss is more significant than for 30-day window advertisers
Recovery: After the deletion, AI Max had to rebuild its model from the remaining data. This may have caused a period of conservative bidding immediately after the deletion — if you saw unusual CPA or ROAS behavior in late June / early July 2026, this is likely why.
DSA to AI Max Migration and Attribution Windows
When migrating DSA campaigns to AI Max for Search (https://yositeup.com/blog/google-ads-dsa-ai-max-migration-february-2027): check your attribution window settings before migration. If DSA was using 30-day windows and your actual cycle is 60 days, the DSA data used to bootstrap AI Max's model also has the wrong attribution window. Extend the window at migration time and import offline conversions to supplement the AI's training data.
AI Max for Shopping and Attribution Windows
For AI Max for Shopping (https://yositeup.com/blog/google-ai-max-shopping-replacing-performance-max-2026): most Shopping conversions happen within 7-30 days (e-commerce is faster than lead gen). The 30-day default is usually appropriate. The exception: high-ticket items in Shopping (furniture, appliances, luxury goods) — extend to 60-90 days if you observe late conversion patterns in your analytics.
To check if you have a late-conversion issue: in Google Analytics 4, look at the "Time to Conversion" report under Reports > Monetization. If a significant percentage of conversions take longer than your current attribution window, you're losing AI signal.
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