An offer listing ID is an alphanumeric token that uniquely identifies an item that is sold by any merchant, including Amazon. Whereas an offer is a combination of Condition, MerchantId, and Price, an offer listing ID is similar to a price tag, one is associated with each item for sale, as shown in the following figure.

This figure shows that three vendors are selling the same item, a shirt. The vendor, labeled Offer 1, has three shirts in stock and each has an OfferListingId.

If an item is for sale, it has an offer listing ID. This ID is returned by the Offers and OfferFull response groups, as shown in the following response snippet.

<OfferListing>
  <OfferListingId>[Offer Listing ID]</OfferListingId>
  <Price>
    <FormattedPrice>Too low to display</FormattedPrice>
  </Price>
  <Availability>Usually ships in 24 hours</Availability>
  <IsEligibleForSuperSaverShipping>0
  </IsEligibleForSuperSaverShipping>
</OfferListing>

Offers contain availability, merchant, and shipping information. If only one merchant is selling an item, the offer response groups return <SingleMerchantId>.

<SingleMerchantId>A304U57TAC62SV</SingleMerchantId> 

<Item>
  <ASIN>B000BWFJQ2</ASIN>
  <OfferSummary>
    <LowestNewPrice>
      <Amount>295</Amount>
      <CurrencyCode>USD</CurrencyCode>
      <FormattedPrice>$2.95</FormattedPrice>
    </LowestNewPrice>
    <TotalNew>1</TotalNew> <TotalUsed>0</TotalUsed> <TotalCollectible>0</TotalCollectible> <TotalRefurbished>0</TotalRefurbished>
  </OfferSummary>