IMPORTANT: June 2017: The OzBargain Referral system is out of beta testing and our main source for referral links. Please use this forum discussion topic for feedback.
On the deal page of merchants that support referral links, you will see a grey box at the bottom of the post (right above share buttons).
These links might benefit some community members who have registered themselves as referrals to these merchants featured on OzBargain. Making purchases through these referral links should not cost you extra. In some cases, discounts or financial incentives apply to both the referrer and referee.
A random link is provided with total number of referral codes in brackets. Clicking on that will pick a random referral link from the pool. If the OP of the deal has their own referral code for that merchant, and the deal gains enough votes to be featured on the front page, there will be a higher chance that the OP's referral link will be selected from the random pool.
As of June 14 2017, users can no longer add their referral link manually in the deal description for merchants already included in the OzBargain referral system. See here for more information.