Ad Valorem, Latin for, "according to value," is a tax placed on the assessed value of real-estate or personal property. These taxes often come in the form of property tax, which is the primary source of revenue for state and municipal governments. Unlike transactional taxes, like a sales tax, Ad Valorem taxes are incurred through continued ownership of an asset.
Ad Valorem as it applies to timeshares is simply the dollar amount in taxes you'll pay on your property, based on the assessment of its value. But remember, because timeshares are divided among multiple owners, so too, will the Ad Valorem tax. Generally, these taxes are to be paid with respect to the owner's specific usage program.