Most PPC conversations start with bids. Lower the bid, raise the bid, try dynamic bids up and down, experiment with a different match type. Those conversations are not wrong, but they treat the symptom rather than the source.
The source of most ACoS bloat is not overbidding on good keywords. It is paying full price to show up for searches that will never convert. A shopper who types "free dog training guide" into Amazon is not buying your premium training collar. Every click you collect from that search is money leaving your account with no path back.
Negative keywords are the fix. They are free to add, take minutes to maintain, and the savings compound every single week. That is why they are the cheapest profit available in Amazon advertising.
The Three Categories of Wasted Spend Negatives Stop
Irrelevant searches
These are the obvious ones. Your silicone baking mat is triggering for "silicone phone case" because Amazon's broad match logic sees the word silicone and takes a swing. The clicks cost the same as your best converter. The conversion rate is zero.
Low-intent informational queries
Searches that include "how to," "what is," "vs," "review," or "DIY" almost never convert at the rate a paid placement needs. The shopper is researching, not buying. You are paying for a branding impression disguised as a transactional click.
Wrong-variant searches
If you sell a 16-ounce version of a supplement, you are collecting clicks from shoppers typing "32 oz" or "family size." Your listing will not satisfy them. The click costs the same; the chance of a sale is close to nothing.
None of these clicks are accidents. They are the natural output of broad and phrase match campaigns doing exactly what they are supposed to do: cast a wide net to find new converting terms. The problem is the net catches trash alongside treasure. Negatives are how you throw the trash back.
How to Find What to Negate
The data lives in one place: the Search Term Report inside Campaign Manager. Download it weekly. Filter to a date range of at least 14 to 30 days so you have statistical signal, not noise.
How to Read Your Search Term Report Like a Strategist covers the full workflow for turning that raw export into clear decisions. For negatives specifically, sort by spend descending and work from the top down. Ask two questions about each row:
- Did this search term produce an order at or below my target ACoS?
- Is this search term relevant to what I actually sell?
If the answer to both is no, it is a candidate for negation. If a term has spent more than a few dollars without a single conversion, that is where you start. Some searches are clearly irrelevant and can be negated immediately. "Free shipping bag" and "how to tie a bowline" do not need a week of data. Others need more spend before you pull the trigger.
The campaign that wins long-term is not the one with the most keywords. It is the one that has been the most ruthlessly honest about which searches it has no business paying for.
Match Type Matters Here Too
Negative keywords follow the same match type logic as regular keywords, and getting it wrong creates new problems.
Negative exact blocks only that precise query. Use it when you want to block "large dog collar" but still show for "large dog collar red" or "large dog collar leather."
Negative phrase blocks any search containing that phrase in that order. Use it for irrelevant root terms. If "how to" never converts on your SKU, add it as a negative phrase and stop paying for every variation of it across that campaign.
Avoid negative broad match for most use cases. It applies too aggressively and can suppress searches you want to own. Negative phrase gives you the control you need without collateral damage.
One structural mistake worth naming: adding negatives only at the campaign level when the issue lives at the ad group level. Campaign-level negatives block the entire campaign. Ad group-level negatives create separation within it, which is useful when you are running tightly themed ad groups and want one group to own a set of terms without the others competing for the same clicks.
Building a Negative List That Compounds
The highest-leverage move is creating a shared negative keyword list and applying it across multiple campaigns. Campaign Manager allows you to create these lists under Bulk Operations. Terms that belong there are the universal irrelevants: competitor brand names you do not want to fund, clearly off-category words, and informational qualifiers that consistently fail to buy.
The list grows over time. Every week you run the Search Term Report review, some terms move to harvest (they are becoming positive exact keywords), some move to the negative list, and some stay on a watch list because they have converted once but not enough to be confident. That weekly cadence is the whole system.
Setting a defensible target ACoS is what makes the negation decision clear in the first place. Without knowing what ACoS you are trying to hit on a given product, you cannot evaluate whether any search term is performing or bleeding. The right approach is covered in deriving target ACoS from contribution margin, and it is worth doing before you run a single negation session.
For brands scaling PPC spend, negation discipline becomes critical at a different scale. A ten percent waste rate at $500 per month in ad spend is a rounding error. At $15,000 per month, it is real money leaving the account every week. The brands running disciplined negation consistently pay less per sale than those who set campaigns and walk away, and that efficiency is a direct path to lower ACoS without sacrificing the spend that actually drives revenue.
What to Do This Week
Pull your Search Term Report for the last 30 days. Sort by spend, descending. Work through every term that has spent more than $5 without an order. For each one, ask whether the shopper typing that exact phrase was ever going to buy your product.
The ones that clearly do not belong: add them as negative phrase or negative exact to the campaigns they are hitting. Create a shared negative list and start populating it with the universal irrelevants that apply across your account.
Set a recurring calendar block, once a week, fifteen minutes. Month one will take longer. Month three will be maintenance. The savings accumulate the entire time, quietly and without fanfare, which is exactly how the best-run accounts stay profitable while everyone else debates what to do about their bids.