Before 1987, mortgage interest on all residences could be deducted without limit. Since then, consumers with more than two residences are required to choose two “qualified” residences where mortgage interest could be deducted, but the selected residences are allowed to be juggled into the “qualified” category from year to year. A home does not actually have to be used to qualify as a selected residence. If there is no rental or personal use of a residence for an entire year, it can be designated as a selected residence and interest can be deducted. If it is rented or used only occasionally by the owner, no interest can be deducted under the personal-residence rule unless there are at least 15 days of personal use.