1. Separate settings from management methods

Amazon offers fixed bids, dynamic bids, and rule-based bidding that adjusts toward a ROAS target. Distinguish these native strategies from an external tool updating base bids using its own rules or ML. Check eligibility in the ad console and inspect placement adjustments as well.

2. Compare fixed and dynamic bidding

Fixed bidding avoids dynamic bid adjustments and lets you inspect the base bid and placement adjustments. Down only can reduce a bid when a sale is judged less likely. Up and down can adjust in both directions based on conversion likelihood, so review both delivery and cost. No setting guarantees a result.

3. Evaluate rules and ML

Amazon rule-based bidding does not guarantee its target. An external conditional rule makes its action easy to inspect, but needs safeguards against reporting delays and small samples. For ML, ask about input data, update frequency, limits, explanations, approvals, and reversal. A method name is not evidence that it is more accurate or profitable.

4. Estimate and review a starting bid

For an illustrative £30 order value, 20% target ACoS, and 5% click-to-order rate, a planning CPC is £30 × 0.20 × 0.05 = £0.30. This is a rough planning value, not a promised auction price or outcome. Revisit conversion assumptions as reporting matures, make bounded changes, and assign one owner so multiple systems do not change the same bid at once.

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