Farfetch offers a special birthday discount to customers who sign up for their loyalty program, Farfetch Access. Members receive a personalized birthday promo code, offering a discount on a range of designer fashion items during their birthday month.
Farfetch Access issues a personalized discount rather than a flat percentage, so what you are offered depends on what you have already spent. Shopbop is the closest comparison for designer stock online. The Iconic covers the same idea in Australia, and Theory is the direct route if you already know the label you want.