Understand collection identifiers

This page describes the identifiers that a Smart Tap collection uses.


Smart Tap is the protocol used between the terminal application and Google Wallet app to convey specific Passes to the terminal.

Here's a summary of the communication flow between the terminal and the Google Wallet app:

communication flow

Google stores IDs to facilitate what to send, but the Pass developer defines what's mapped. There's also some configuration required at the terminal to recognize what's mapped.

Because a merchant might use various businesses or contractors to develop their Passes, we use three IDs to facilitate the collection of Passes. This allows a merchant who uses a particular terminal provider to redeem Passes from many Pass developers.

The following three IDs are used to set up terminal collections of correct Passes via Smart Tap:

  • Redemption issuer ID
  • Collector ID
  • Pass class ID

Issuer ID

The issuer ID is the unique identifier of a Google Wallet API account. You can find the issuer account in your Google Pay and Wallet Console.

An issuer account can represent a merchant such as a restaurant, an offer provider, or a terminal manufacturer. When Pass classes and objects are developed, they're contained under the issuer ID. An issuer ID can have as many class IDs as needed.

An issuer account can only have a maximum of one collector ID. To assign the issuer ID its collector ID or to create a new issuer ID, see Enable Smart Tap for a merchant.

Redemption issuer ID

A redemption issuer ID is a specific type of issuer ID. A redemption issuer ID typically represents a single merchant. In contrast, an issuer ID for a Pass developer might represent their platform, which stores classes for many different merchants.

A redemption issuer has a collector ID if the merchant supports Smart Tap at their terminals. That's how terminals request specific Passes. See Understand how a terminal requests Passes to learn more.

Collector ID

The collector ID is the numeric ID that the terminal uses to identify itself. It's typically eight digits. In practice, the collector ID defines the merchant, and all the terminals in each merchant’s store have the same collector ID.

When a Smart Tap occurs, the terminal sends a collector ID to the mobile device. The mobile device then attempts to authenticate the terminal with any public keys it has that are related to that collector ID.

Only one collector ID is assigned to an issuer ID, and the collector ID is unique across all Issuer IDs. To assign an issuer ID a collector ID, see Enable Smart Tap for a merchant.

Pass class ID

A Pass class ID identifies a particular tier, or type, of Pass. For example, “Gold member loyalty card for Baconrista.” An object of this class is saved and shown in the Google Wallet app. Note that an object is a particular Pass meant for a specific user. See Classes and objects for more details.