Accrued 23 days of leave on an ADOS Tour, what is the process to sell back this leave while being back in the Army Reserves?

Your UA or RPAC needs a copy if your LES, and you will also need to sign the request to be paid your days. Then your YA/RPAC will send a transmittal letter to the pay team to have it paid out

Be sure that you want to sell the days! You can only sell 60 days in your career. If you can get your orders extended to use your leave it’s better to use it.

Are you still on orders? If so, see if you can get them amended so you can take those leave days. If you sell them you are leaving money on the table in the form of BAH/BAS. If you're already off orders you'll need a copy of your orders and there's a form you have to sign. your UA should have the form and then they can submit a request to get you paid for those days.

Also, if I remember correctly, you would earn retirement points for those days of leave it you got your orders amended to take them instead of selling them. I did that my last ADOS tour. I accrued 16 days of leave and got my orders extended to take them.