Photo by Carlos Muza on Unsplash (photo)
Performance Max campaigns promised to revolutionise Google Ads. For many UK businesses, they've delivered impressive results. For others? They've become a black box of wasted budget and confusing attribution.
Here's the reality: Performance Max isn't broken. Your setup probably is.
After conducting dozens of Google Ads audits throughout 2026, we've spotted the same mistakes appearing again and again. The good news? They're fixable. Let's walk through the seven most common Performance Max errors and exactly how to correct them.
1. You're Starving the Algorithm with Limited Assets
The mistake: You've uploaded five headlines, three images, and called it a day. The algorithm has nothing to work with, so it's showing the same creative repeatedly, and your audience is tuning out.
The fix: Build a comprehensive asset library with at least 15 headlines, 15 images, and multiple videos. This isn't a one-time task. Treat asset creation as an ongoing process, refreshing your creative every 6-8 weeks.
For video specifically, create at minimum one 15-second video per asset group in both horizontal (16:9) and vertical (9:16) formats. Skip Google's auto-generated videos, they consistently underperform compared to purpose-built content. Your phone camera and basic editing software will produce better results than relying on automated creation.
Photo by Luke Chesser on Unsplash (photo)
2. You're Panicking During the Learning Phase
The mistake: Your campaign launched three days ago. Performance looks mediocre. You've already changed your bid strategy, adjusted budgets by 50%, and added new conversion actions. Now the learning phase has reset, again.
The fix: Set your campaigns up correctly from the start, then step away from the keyboard for 4-6 weeks. Every substantial change, budget adjustments above 20%, bidding strategy modifications, or conversion action updates, completely resets the learning period.
Think of machine learning like teaching someone to drive. If you grab the wheel every 30 seconds, they'll never learn. Give the algorithm time to understand your business before intervening.
3. Your Conversion Tracking Is Lying to You
The mistake: You're tracking everything as a conversion, form views, button clicks, scroll depth, page visits. Or worse, the same conversion is firing multiple times per transaction. Your data is polluted, and the algorithm is optimising toward junk.
The fix: Conduct a thorough conversion tracking audit by:
- Verifying each conversion fires only once per genuine transaction
- Assigning accurate monetary values to all conversions
- Excluding internal traffic and testing
- Implementing server-side tracking for improved reliability
Apply conversion data consistently across your entire Google Ads account. Use the same attribution methods, count types, and conversion windows. Inconsistent tracking confuses the algorithm and skews your performance data beyond recognition.
4. Your Target ROAS Is Living in Fantasy Land
The mistake: You're currently achieving 300% ROAS. You've set your target at 500% ROAS because "ambitious goals drive results." Your campaign now barely spends because insufficient inventory exists at that efficiency level.
The fix: Set initial targets within 20% of your current actual ROAS. If you're hitting 300%, start at 360%. Once performance stabilises, increase targets in 10-15% increments over 4-week intervals.
The same applies to CPA targets. If campaigns aren't spending, relax aggressive CPA targets by 20-30%. You can gradually tighten them as the algorithm finds efficiencies, but starting too aggressive simply chokes delivery.
Photo by Campaign Creators on Unsplash (photo)
5. You're Getting Fooled by Attribution Inflation
The mistake: Your Performance Max campaign shows brilliant ROAS, but your overall business revenue hasn't grown. That's because Performance Max is over-indexing on retargeting and existing customers, creating a feedback loop that reinforces spend on people who would have converted anyway.
The fix: Verify whether Performance Max is driving genuine incremental growth by checking these signals:
- View-through conversions exceeding 60% (major red flag for attribution inflation)
- New versus returning customer ratios heavily skewed toward returning
- Revenue that doesn't correlate with campaign spend increases
Switch to click-only conversion tracking temporarily to measure true click-driven performance. For the ultimate test, pause Performance Max for two weeks and measure actual business impact. Yes, it's uncomfortable. But if revenue barely dips, you've just discovered your campaign was taking credit for organic demand.
6. You've Created Too Many Campaigns Without Enough Data
The mistake: You're running 12 separate Performance Max campaigns with 200 monthly conversions split across them all. Each campaign receives insufficient data for effective learning, so none of them optimise properly.
The fix: Follow the "30 conversions per campaign monthly" rule. If you lack sufficient conversion volume, consolidate campaigns and use asset group segmentation instead.
Conversely, avoid creating a single mega-campaign with eight asset groups. This approach limits budget allocation flexibility. Instead, use a multi-campaign structure with one asset group per campaign. This gives the algorithm more control over budget distribution between your different audience segments or product categories.
7. You've Abandoned Everything Else for Performance Max
The mistake: You've paused all Search and Shopping campaigns, putting everything into Performance Max. Now you've lost the benefits of campaign type diversity and eliminated your ability to capture high-intent branded searches with specific messaging.
The fix: Run Performance Max alongside traditional campaigns in a complementary structure:
- Maintain exact-match brand Search campaigns to protect your brand terms
- Keep high-performing Shopping campaigns running for products with proven profitability
- Use Display for remarketing with specific promotional messaging
- Let Performance Max focus on discovery and audience expansion
This hybrid approach captures immediate demand whilst allowing Performance Max to explore new opportunities. It also provides a performance benchmark: if Performance Max significantly underperforms your traditional campaigns long-term, you've identified a setup issue.
Photo by Hunters Race on Unsplash (photo)
The Bottom Line on Your Google Ads Audit
Performance Max succeeds when fuelled by strong, reliable data and strategic setup. It fails when treated as a "set it and forget it" solution that requires no oversight or optimisation.
If you're unsure whether these mistakes are affecting your campaigns, a comprehensive Google Ads audit will identify exactly where you're losing efficiency. At The Digital Academy, we offer a free digital marketing assessment that analyses your Google Ads setup, identifies optimisation opportunities, and provides a clear action plan for improvement.
The difference between a Performance Max campaign that drains budget and one that drives profitable growth often comes down to these seven fundamentals. Review your setup against this checklist, make the necessary corrections, and give the algorithm the foundation it needs to deliver results.
Your competitors are making these mistakes right now. You don't have to.
