@gary-gena-davis Hello, I can shed some light on this question as well:
HomeAway (and other channels) are very strict on the content that can be sent to a customer while they are still a pre-booking or inquiry state. You'll notice additional things like the customer's email are filtered - this is done by HomeAway to prevent any possibility of a booking being taken off their platform and booked independently, and taking away their cut of the booking. HomeAway filters out links as well, so when you're making quote changes within MyVR, the renter isn't receiving any sort of updated payment link to pay the new quote.
That being said, after the renter commits and completes the booking, HomeAway is no longer strict about their messaging, and you would be able to send a revised quote. Here's how I recommend you handle this situation given HomeAway's restrictions:
Have the renter navigate to your listing again and submit an inquiry for the correct dates
Have them complete the booking with the correct set of dates, they would need to pay your full standard rate
Once they have completed the booking, you would now be able to adjust the quote to reflect the discount, and the customer would be automatically refunded
One possible workaround would be to configure the rental rates for the property in a way that the customer wouldn't need a separate discount (creating custom rates.) That way when the customer makes an inquiry for those dates, the final price you intend to be charging them is already being reflected.