Bidding rule

A Bidding rule acts on line items: “Change a line item’s max bid, or pause or enable it, when its numbers match the conditions.” Create one under Automation Rules › Bidding › New Rule.

When

Setting	What it does
Line items	All line items, Performance+ only or Standard only
Look back (days) · Skip latest days	The window the conditions are measured over
Minimum impressions	Line items with fewer impressions in the window are not checked
All of these are true	At least one condition, up to 10

The conditions and the window are described in The parts of a rule.

Only line items that are Enabled or Paused are checked, and a line item that started less than 7 days ago is left alone while Amazon is still learning: “Line item is still learning (under 7 days)”.

Then

Action	What it does	Limits
Change max bid by %	Raises or lowers the max bid (maximum average CPM) by a percentage. Running line items only	Raise up to 500%, lower up to 90%. Lowest max bid and Highest max bid, $0.01 to $1,000
Set max bid to a value	Sets the max bid to the amount you enter. Running line items only	$0.01 to $1,000
Set max bid to Automatic	Lets Amazon set the bid for each impression. Running line items only	Applied only by hand from Preview
Pause line item	Pauses a running line item	—
Enable line item	Enables a paused line item	—

Changing the max bid by a percentage

The new bid always stays between the rule’s lowest and highest max bid — but the rule never moves a bid the wrong way to get there. A rule that lowers bids leaves alone a bid already below its lowest limit, and a rule that raises bids leaves alone one above its highest. Those rows read “Already at the target”.

A line item on Automatic max bid has no CPM to change, so it is skipped: “Max bid is Automatic”. Set max bid to a value does apply to it.

Setting the max bid to Automatic

“Automatic removes the CPM cap, so scheduled runs never send it: apply it by hand from Preview.” Its rows appear in Preview and Runs; a run logs them as “Automatic max bid is applied only by hand from Preview”.

Pause and Enable

“Only running line items are paused. Automation never archives or deletes anything.”

“Only paused line items are enabled, judged on their numbers before they were paused.” A paused line item has no new numbers, so an Enable rule uses its usual window and only the days before the pause that fall inside it count. A line item paused for longer than the window has no numbers there and isn’t checked. This includes line items you paused by hand: exclude a line item you paused on purpose, or an Enable rule may turn it back on. Switching on an Enable rule warns about this.

When a rule pauses a line item, nothing else changes on that line item in the same run — not its max bid, frequency cap or spend cap.

Cooldown

“After Automation changes a line item, this rule waits this long before changing the same thing again.” 0 to 90 days. A new rule starts at 3 days for max bid actions and 7 days for Pause and Enable, so a line item is not paused and enabled back and forth.

Starting values

A new Bidding rule opens with: all line items, the last 14 days skipping the latest 3, at least 1,000 impressions, ROAS ≤ 1, lower max bid by 10% within $1 to $20, cooldown 3 days. Change them before you save.

New rules start switched off.