When a guest has booked your property on Airbnb and the 20% promo discount have been applied to the booking, this will be reflected in the booking as well.
This special discount will be itemised in the financial information of the booking.
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The discount is also showing when you click to Edit in any booking.
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In the pop-up scroll down until the Other discount field is showing.
Please note:
Should the pop-up not open, make sure that you disable the pop-up blocker in your browser.