ACoS is a ratio, so it moves when either half moves. **Spend up** and **sales down** look identical on the headline number and need opposite responses — which is why the first step is never "look at the campaigns".

This is a fixed order. It takes ten minutes and it ends with a cause, not a suspicion.

[Watch the walkthrough](https://kb.trackiq.com/kb-assets/kbvideo-acos-spike-explainer-228be5f4.mp4)

*Prefer to watch? Eighty-six seconds on splitting the ratio before you open a single screen.*

## **Step 0 — Split the ratio**

Before opening anything, answer one question: **did spend rise, or did sales fall?**

Any screen with the **Values / % change** toggle will tell you. Set the range to the spike, compare against the previous period, and look at spend and ad sales separately.

| What moved | Where to go |
|---|---|
| Spend rose, sales roughly flat | step 1 — a bidding or budget change |
| Sales fell, spend roughly flat | step 3 — a conversion or availability problem |
| Both moved | do step 1 first, then step 3 |

Skipping this step is how people spend an afternoon auditing keywords when the actual cause was a listing that went out of stock.

## **Step 1 — Check what you changed**

**Automations → the rules list.**

Scroll right to **Last Run** and **Changed**. A rule that touched several hundred entities the night before the spike is your first suspect, and it takes fifteen seconds to check.

Open its **Run History**, find the run covering that date, and **View** it. Every changed entity is listed with the branch that fired and the value before and after. If bids across a group went up 15% that morning, you have your answer without leaving the screen.

See [**Scheduling: Last Run, Next Run and Run History**](https://kb.trackiq.com/hc/knowledge-base/articles/rule-scheduling-and-run-history).

**Also check the Change Log** for anything a person did. Between the two, most spend-side spikes are explained inside two minutes.

## **Step 2 — Find where the spend went**

**Amazon Ads → Campaigns.**

![Campaign performance with the comparison toggle](/kb-assets/shot-adv-campaigns-view-77ace2.png)

Set **vs previous** and switch to **% change**. Sort by spend change, descending.

You are looking for **concentration**. Almost always, one or two campaigns account for most of the increase. If the rise is spread evenly across everything, that is a market-level change — competitors bidding up, or a seasonal shift — and it is a different conversation.

Once you have the campaign, go one level down to its ad groups, then to keywords and targets. Keep asking the same question: *is this concentrated or spread?*

## **Step 3 — If sales fell instead**

Spend-side causes are easy. Sales-side causes are the ones that matter more, and they are rarely in the advertising at all.

**Check availability first.** An out-of-stock or suppressed listing stops converting while the ads keep spending. This is the single most common cause of a sales-side ACoS spike. See [**Catch a stockout before it costs you rank**](https://kb.trackiq.com/hc/knowledge-base/articles/catch-a-stockout-early).

**Then check conversion.** In **Search Query Performance**, look at your click share against your purchase share on your main terms. Clicks holding while purchases fall means people are arriving and leaving — a price change, a review slide, a competitor promotion. See **Search Query Cart Analysis**.

**Then check rank.** A slide in organic position means you are paying for traffic you used to get free. **Rank Tracker** dates it.

## **Step 4 — Look at the query mix**

**Amazon Ads → Search Terms**, aggregated.

![Search terms aggregated across the account](/kb-assets/shot-adv-terms-view-2cadd4.png)

A spike with no obvious campaign cause is often a **mix** change: broad or auto targeting started matching new queries, and those queries convert worse than the ones you were getting.

Sort by spend change. New high-spend terms that did not exist last period are the tell. Negative-match the ones that clearly do not fit, and check whether a match-type change or a bid rise widened the net.

## **Step 5 — Confirm before you act**

Two checks that stop you fixing the wrong thing:

**Attribution lag.** Recent days under-report sales — up to 7 days for Sponsored Products, 14 for the other formats. A "spike" in the last two days is very often incomplete data. Re-check with the freshest days excluded before touching anything. See [**Why SP, SB and SD Numbers Don't Add Up**](https://kb.trackiq.com/hc/knowledge-base/articles/why-sp-sb-and-sd-numbers-dont-add-up).

**Is it actually a spike?** Compare to the same period last month and, if you have it, last year. Some of what looks like a spike is a weekday pattern or a seasonal one.

## **What good looks like**

You finish with a sentence, not a feeling: *"spend rose 40% because the bid rule raised bids on the generic group on Tuesday, and those terms convert below break-even."*

If you cannot write that sentence, you have not finished — and changing bids before you can is guessing with money.

## **What not to do**

**Do not cut budgets first.** It lowers spend and ACoS while lowering sales too. It hides the cause rather than fixing it.

**Do not blame the rule without checking it.** Open the run. The rule may have done exactly what you asked; the problem may be the threshold you set.

**Do not react to one day.** Daily ACoS is noisy on any account below serious volume.

**Do not fix two things at once.** You will not learn which one worked.

## **Related**

- [**Understanding ROAS and Key Amazon Advertising Metrics**](https://kb.trackiq.com/hc/knowledge-base/articles/understanding-roas-and-key-amazon-advertising-metrics) — what ACoS is measuring.
- [**Scheduling: Last Run, Next Run and Run History**](https://kb.trackiq.com/hc/knowledge-base/articles/rule-scheduling-and-run-history) — step 1.
- [**Values vs % Change: The Comparison Toggle**](https://kb.trackiq.com/hc/knowledge-base/articles/values-vs-percent-change) — step 0.
- [**Cut wasted ad spend in an afternoon**](https://kb.trackiq.com/hc/knowledge-base/articles/cut-wasted-ad-spend) — what to do once you have found it.
- [**The Bleeder Reports**](https://kb.trackiq.com/hc/knowledge-base/articles/the-bleeder-reports) — when the cause is a target bleeding rather than a market shift.
- [**Placement Bid Optimisation**](https://kb.trackiq.com/hc/knowledge-base/articles/placement-bid-optimisation) — when the cause is spend sitting on the wrong placement.