They posted info on the new ticket exchange for STHs this year called "Fluid Tickets":
Can’t attend a game? Don’t let your tickets go unused. You can:
Post your ticket(s) for resale, transfer to a guest via the Bucks App,
OR
Turn in your ticket(s) for Bucks Credits good toward: future mobile seat upgrades or additional mobile tickets for upcoming games in your membership
How:
Download the Bucks App, select “Upgrade Your Experience” from Tickets icon, login and visit the “Fan Hub” tap “Return Seats”, and then "Earn Experience Credit". We’ll provide you with a Bucks Experience Credit equal to the face value of the ticket(s) you turn in. Seats are then released from your account and made available for other fans to purchase or upgrade into.
Q&A
Q: What is Bucks Credit?
A: Bucks Credit (referred to as Experience Credit) is the value a Full Season Member receives when he/she returns tickets for a game they will not be attending. Members must return tickets using their mobile phone no later than 4 hours prior to tipoff through the Bucks app to earn Bucks Credit. These credits have no cash value and are not transferrable. Credits also expire at the conclusion of the regular season.
Q: What is the “Return Tickets” feature?
A: “Return Tickets” is a ticket management feature that allows you to return tickets for games you’re not attending in exchange for Bucks Credits that can be used for seat upgrades, or to add tickets for a future game. Tickets must be returned prior to the start of the game.
Q: How do I return my tickets for Bucks Credit?
A: Download the Bucks App, tap on Upgrade your Experience, and login with the primary email address tied to your season ticket membership. At that point, you’ll be able to register, establish a PIN and then select games to return in exchange for Bucks Credit.
Q: How many times can I use this feature to return my tickets for Bucks Credits?
A: Full Season Members can use “Return Tickets” as much as they like.
Q: Can I return tickets to a game at the end of the season today?
A: Yes, however the tickets for the game(s) you wish to return must be paid in full. If you know you will not be attending, you may also use any of the transfer, donate to charity, or post for resale options on Account Manager.
Q: What is the deadline to exchange my seats by in order to receive credit?
A: If the “Return Tickets” feature is still active for a game and you can’t attend, tickets may be returned until 3 hours prior to tipoff. Please note that the value of received for the return is dependent on when you return.
Q: Once I’ve returned tickets, how do I use my Bucks Credit to purchase a seat upgrade, or add tickets for a future game?
A: Download the Bucks App and register for notifications to an upcoming game(s). Seat upgrades will be available when doors open on the day of the game.
Q: Can I use my credit to pay off my current season ticket balance or use toward renewal of my membership?
A: Bucks Credits have no cash value, cannot be transferred or applied to your current ticket package or toward season membership renewal and/or playoffs. Credits are intended to enhance your experience for another game in your package.
Q: Can I redeem Bucks Credit for cash value?
A: No. Bucks Credit does not have any cash value.
Q: Does Bucks Credit expire?
A: Yes. Any Bucks Credit accumulated during the 2018-19 regular season will expire on April 11, 2019.
Q: Are Bucks Credits transferrable?
A: No. Bucks Credit is non-transferable and is only associated with the primary member’s email address.
Q: What happens to my original seats?
A: Your original seats are returned to the Bucks and may be used by fans who are purchasing seats or upgrading their seats during the game.
Q: Can I sell my tickets via Account Manager or NBATickets.com after returning tickets?
A: No, your barcodes will be deactivated after selecting “Return Tickets”. This is not reversible.
Q: I used “Return Tickets” but then decided I can attend the event. Can I cancel my return and get my original seats back?
A: No. All transactions are final.
Q: If I only plan on using two of my four seats for a given game, can I return the other two seats?
A: Yes, you can select which specific seats are returned and exchanged for Bucks Credits.
Q: Can I exchange games over the phone or through email?
A: No. You may only return tickets and exchange for Bucks Credits through the Bucks App on your mobile phone.
Q: How can I view my credit balance?
A: You can view your current Bucks Credit balance in the Fan Hub section of the Experience homepage located in the upper right corner.
Q: Can I extend the ability to return tickets or use credit for a share partner?
A: No. The ability to return tickets and use Bucks Credit is assigned only to the email address of the primary member.
Q: Will my original ticket(s) scan in once I have selected “Return Tickets”?
A: No. The barcode(s) on your original ticket(s) are deactivated and become invalid for entry to Fiserv Forum.
Q: If I emailed my tickets to a friend and then they can’t go and email those tickets back to me, can I return those for credit?
A: No. Since the ticket (and the original barcodes) have been change, the ability to return these tickets is deactivated.
A little confusing because at first they say: "We’ll provide you with a Bucks Experience Credit equal to the face value of the ticket(s) you turn in." but in the Q&A: "Please note that the value received for the return is dependent on when you return" implying that you could receive less than face value under certain circumstances.
Also this system doesn't appear to be functional yet.