Fashion brands have to place large orders for stock to ensure they have enough coverage to attain sales without selling out. Often sample sales are an avenue for brands to sell the excess stock that didn't sell through when it was in retail stores, or on online stores; or sell pieces from the runway or samples that have been created during the development and production process. In order to reduce wastage and to be more sustainable, brands look to sample sales to sell this excess stock  with aggressive discounts (sometimes reaching 90% off its original retail price). Brands do not hold sample sales regularly and are often a flash sale which only last for a matter of days. Some sales are for exclusive groups of people, whilst others are open to the public but require a reservation but then there are those you can walk into and shop. Do remember that some brands market sample sales under other names. Popular names are 'outlet sales'; 'warehouse sales'; 'private sales', and more.