A default address allows your items to be returned directly to you in the event that the carrier marks them as undeliverable, or if they are returned for any reason.
To add a default address, simply tap 'Addresses' in the app's menu then 'New delivery address'. You'll be able to add a label such as home or work, and toggle an address to be your default delivery address.
If you do not have a default address on file and your items are returned by the carrier, they'll be retuned to our warehouse. They'll be reprocessed and our Customer Experience team will reach out to you to let you know, but this will take more time compared to the items just being returned to you directly.