Looking for a replacement for the long-running MASTERAU12 coupon I found this - MASTERAU11…
I can't find it on the official Mastercard website yet, but the code seems to work if you click through the link in this post (I found the code and link on Couponation FWIW).
TERMS AND CONDITIONS OF EXPEDIA MASTERCARD VOUCHER OFFER
Qualifying Bookings: This coupon code discount (“Coupon”) applies only to stand-alone hotel bookings (not a hotel booking in combination with any other product or offering such as flight + hotel or flight + hotel + car) made online at www.expedia.com.au/mastercard that are prepaid at the time of booking (subject to the restrictions set out in the Terms and Conditions below). You must make payment using a valid MasterCard credit card issued in Australia to qualify for this offer. (“Eligible Card”).
Coupon code value: 11 % discount (“Discount”).
Redemption Period: Valid for use by 11:59pm AEST, 31 December 2018 (“Redemption Period”).
Travel Period: The travel dates must be before 30 June 2019 (“Travel Period”).
How to use your coupon code
• During the booking process, on the payment page you will see the link ”Enter coupon code” where you can enter the coupon code;
• Enter the coupon code in the relevant field and then click the “Apply Coupon” button. If your booking is eligible, the applicable discount will be subtracted from the price of the travel reservation before the application of any taxes, applicable fees or additional costs.
• Use an Eligible Card to pay for your qualifying booking.
• This offer does not apply for multi-room bookings.
(EDIT: fixed the link - should go directly to a valid link for the coupon now - banner should appear on the top of the page)