Download or open the Booking.com app, go to Wishlists, heart 3 properties and get $15 $20 credit. Easy.
Android(play.google.com) - iOS(apps.apple.com)
"Liking" involves tapping the heart icon on a property. The credit expires in August 2021.
via toyocoro at OzBargain(ozbargain.com.au)
I got $20 NZD credit
Had to update app to latest version first