You'll need to specify what type of Guarantee your speaking of.
The guarantee given for your products should be getting a reserve accrual for anticipated claims, which is certainly a BS item.
Most direct Guarantees given for financial reasons, as in Ging an affiliated Co so they can use some of your better Cos credit rating, or any G that impairs the available credit line other wise avail - even if it doesn't have a money cost involved - (which most all do), likewise has a balance sheet effect.