Where Google Ads budgets actually leak: a UK advertiser's checklist
Wasted ad spend is rarely one dramatic mistake. It's usually seven small ones, each individually defensible, compounding quietly month after month. Here's where to look, in the order that tends to pay best.
Every account audit starts the same way: find the money that's leaving without a job to do. The list below is roughly the order I work through, because it's roughly the order of expected return. Each item includes where to find it in the Google Ads interface, so you can check your own account before deciding whether you need anyone's help.
1. Broad match keywords with no negative keyword discipline
Broad match is genuinely better than it was five years ago, because it now reads intent rather than just matching loosely related words. It is still the single largest source of wasted spend in most accounts, for one reason: it will keep finding new queries forever, and some proportion of them will always be wrong.
The failure mode isn't using broad match. It's using broad match and then never looking at the search terms report again.
Where to look: Campaigns → Insights and reports → Search terms. Set the date range to the last 90 days, sort by cost descending, and filter to conversions = 0. Anything expensive with no conversions and no plausible route to one is a negative keyword candidate.
What it's typically worth: In accounts that have never had a systematic search-term review, 10–25% of total spend. It's not unusual to find a single irrelevant query family — job seekers, DIY researchers, people looking for free versions of what you sell — consuming four figures a month.
2. Performance Max eating your brand traffic
Performance Max will happily serve against searches for your own company name, then take credit for conversions that would have happened anyway. The reported ROAS looks superb. The incremental value is close to zero — you were going to get those customers for a fraction of the cost through a dedicated brand campaign, or free through organic results.
This is the most common way a "high-performing" account is quietly overpaying.
Where to look: Compare your brand campaign's impression share over time against your Performance Max spend. If brand impression share fell as PMax ramped up, PMax is taking the traffic. In the PMax campaign, check the search themes and the asset group insights.
What to do: Add brand terms as account-level negative keywords excluded from Performance Max, and run brand as its own low-CPC Search campaign where you can see and control it. Google now allows brand exclusions on PMax — use them.
3. Conversions being counted more than once
If one form submission fires two conversion actions — say a Google Tag Manager trigger and a GA4 imported event — your cost per conversion looks half what it really is. Bidding algorithms then chase phantom performance, and you make budget decisions on numbers that were never true.
The variant of this that costs most: counting a soft action, like a page view or a click on a phone number, as a primary conversion alongside actual enquiries. Smart bidding will optimise toward whichever is easiest to generate, which is always the soft one.
Where to look: Goals → Conversions → Summary. Check which actions are set to Primary — only genuine business outcomes belong there; everything else should be Secondary. Then check the "Count" setting: lead-generation actions should usually count One per click, not Every.
What it's typically worth: This rarely shows up as a direct saving. It shows up as every other decision in the account becoming correct.
4. Location settings quietly targeting the world
Google's default location option is "Presence or interest: people in, regularly in, or who've shown interest in your targeted locations." For a UK plumber, that means paying for clicks from people in other countries who have shown interest in the UK.
Where to look: Campaign → Settings → Locations → Location options. Set it to Presence: people in or regularly in your targeted locations. Then check Reports → Locations → User locations to see where your clicks physically came from.
What it's typically worth: For locally-delivered services, frequently 5–15% of spend, and it's a one-minute fix.
5. Search campaigns opted into Display and Search Partners
When you create a Search campaign, Google pre-ticks the Display Network and Search Partners boxes. Display inventory bought through a Search campaign converts far worse than Search inventory, but shares the budget with it, so it drains money from the thing that works.
Search Partners is more debatable — for some advertisers it performs acceptably. The point is that it should be a decision, not a default.
Where to look: Campaign → Settings → Networks. Untick Display Network. Segment your data by network before deciding on Search Partners.
6. Device performance nobody has looked at
Mobile traffic is cheaper per click and frequently far worse per conversion, especially for B2B and for anything requiring a considered purchase. Averaged together, the account looks fine. Split by device, it often turns out desktop is subsidising mobile.
Where to look: Campaign → Insights and reports → When and where ads showed, or add the Device segment to your campaigns table. Compare cost per conversion across mobile, desktop and tablet.
What to do: With smart bidding you can't set hard device bid adjustments the way you used to, but you can still apply a -100% adjustment to exclude a device entirely, or split campaigns by device where the difference is severe enough to justify the added complexity.
7. Budget-capped campaigns that should be uncapped, and vice versa
Two opposite errors, both common. The first: a campaign that converts profitably is capped by its daily budget and losing impression share — you're leaving money on the table rather than wasting it, but the effect on the P&L is the same. The second: a campaign that doesn't convert has plenty of budget and spends all of it.
Where to look: Add the columns Search impression share, Search lost IS (budget) and Search lost IS (rank) to your campaigns view. High lost-IS-to-budget on a profitable campaign means increase the budget. High lost-IS-to-rank means the problem is bids or quality, and more budget won't help.
Doing these in the right order
Fix conversion tracking first, even though it's third on the list above, because everything else is measured with it. An account where the tracking is wrong will produce confident, well-reasoned, incorrect conclusions from every other item here.
After that: negatives and search terms, because that's where the largest recoverable pound figure usually sits. Then settings hygiene — locations, networks, devices — because those are quick and permanent. Then structural work like brand separation and budget reallocation, which take longer to prove out.
What's realistic to recover
In a UK account that hasn't had specialist attention for six months or more, 15–30% of spend is typically recoverable or redeployable. That doesn't mean the budget shrinks by a third — it usually means the same budget produces meaningfully more conversions, because the money moves from queries that never converted to ones that do.
Accounts already managed competently are a different story. There, the gains come from structure, tracking sophistication and bidding rather than from finding obvious waste, and improvements are measured in single-digit percentages compounding over quarters. Anyone promising a 30% improvement on a well-run account is guessing.
The uncomfortable version of this checklist: most of it takes an afternoon, and most accounts have never had that afternoon spent on them.
If you'd rather not do it yourself
The free account review runs this checklist against your account and puts a number against each item. Read-only access, a written summary, no obligation to buy anything afterwards.