A primary or principal residence is determined by where someone lives the majority of the time. A home where you spend weekends and vacations is considered a secondary residence. A rental property is also classified as a secondary residence.
A primary residence can be switched if an owner decides to spend more time at a residence that was previously his secondary residence. The Internal Revenue Service (IRS) requires proof of your primary residence for tax purposes.
Primary and secondary home real estate taxes are usually deductible. Mortgage interest on primary and secondary homes is also deductible if the mortgage meets the requirements established by the IRS.
According to the IRS, mortgage interest can only be deducted if your mortgage is considered secured debt. Qualified structures include any mortgaged structure that has a kitchen, bathroom and sleeping quarters. It can be a house, house trailer, houseboat, mobile home or condominium.