Brand halo (halo sales)

Halo means different things per ad type, and the definitions are not interchangeable. Amazon Attribution counts only products of the same brand as the promoted product, in separate "BH" columns on a 14-day click window. Sponsored Brands and Sponsored Display share one rule in Amazon's documentation — products on the campaign's landing page, plus any other products from those same brands. Sponsored Products for sellers is the odd one out: Sales (halo) is simply sales within 7 days of a click where the purchased SKU was other than the one advertised, bounded by the merchant's own catalog, with no brand test at all. Vendors get no promoted-versus-halo split on that report, only an undifferentiated 14-day Sales.

The received wisdom — halo is hidden, so add it back to ACoS — is backwards and double-counts. On the seller advertised-product report, Sales is the 7-day total and Sales (promoted) and Sales (halo) are its two subsets; the console's ACoS and ROAS already run off that total. The real risk is the inverse: a campaign showing comfortable ACoS whose advertised ASIN barely converts, the win being variation or repeat demand you already owned. Compute Sales (halo) divided by Sales per campaign and treat high-halo campaigns as unproven rather than as hidden winners. Amazon warns that tracking ASINs for multiple brands in the same campaign can result in an expansive brand halo and unexpectedly high T-ROAS — that applies where you track ASINs, in DSP and Attribution, not to a seller's Sponsored Products campaign.