If you rented the timeshare as a business, you can deduct this expense as a loss on your investment.
If your timeshare was for personal use only, you cannot deduct costs associated with exiting a timeshare.
The IRS classifies timeshares as personal property, like a boat or motorhome. So, you can't deduct the mortgage interest or property taxes on your timeshare like you can with a primary residence or second home. You also can't write off the cost of your deeded timeshare when you eventually sell it.