Non-Stacked (sometimes referred to as “Standard”) indicates that the coverage’s total limit is the limit displayed on the declaration page for that unit. For example in a scenario where the insured has Non-Stacked Underinsured Motorists Coverage on two units, each with a $100,000 limit, then the insured would be covered up to a maximum of $100,000 for Underinsured Motorists (i.e. the $100,000 for unit 1).
Stacked (sometimes referred to as “combined”) indicates that the available limit is the aggregate of the limits displayed for all units on the policy for that coverage. For example in a scenario where the insured has Stacked Underinsured Motorists Coverage on two units, each with a $100,000 limit, then the insured would be covered up to a maximum of $200,000 for Underinsured motorists (i.e. the aggregate of $100,000 for unit 1 and $100,000 for unit 2).
See policy forms for full details.