A piece of data not available as a standard when an affiliate programme is set up, but that can be added as an additional field to aid optimisation within the tracking tag. This data is then passed into the network reporting, the data is often accessed as an additional field in reports or can be used for the purposes of commission setting/validations.
Example: A travel retailer might choose to pass the number of nights or the date of stay in a hotel, or an ecommerce brand could choose to pass whether a sale is from a new or existing customer.
