Leakage refers to any way in which an affiliate may lose commission due to an untraceable action on the merchant’s website. Examples include:

• A customer is referred by an affiliate but completes the transaction by telephone.
• A customer follows a link to another website owned by the merchant, and completes a transaction there which is not tracked.
• A merchant encourages a customer to sign up for an e-mail newsletter on their site, and uses tracking within it that conflicts with affiliate tracking (for example overwriting cookies or deduping sales). See Affiliate Tracking & Data for more information

The following are best practice guidelines for avoiding commission leakage. Ideally these should be considered before launching a program.

1. If a phone number is displayed on the merchants site through which orders can be placed, this must either be removed or made far less prominent for affiliate traffic. Alternatively, a method should be used to reward affiliates for customers they refer who place orders by phone. Customer service numbers in ‘help’ or ‘contact us’ sections of websites are fine.

2. If a merchant refers customers to another website owned by themselves through which a purchase can be made, these sales should be tracked and commission awarded. A good method of doing this is to setup an affiliate programme for the linked website, and allowing cross-tracking of sales.

3. The merchant should reduce any chance of customers leaving their site before making a purchase, particularly for affiliate traffic. Excessive links, banners and other forms of advertising linking to other sites therefore need to be minimised for affiliate traffic.

4. If a customer is encouraged to sign up for other marketing channels, such as an e-mail newsletter, commission leakage as a result should also be avoided. Separate tracking systems should be used if a customer clicks through from an e-mail, the affiliate cookie should still stand, and sales should not be deduped against the affiliate channel.