Q: You wrote a story that said any mortgage interest for periods of "personal use" of a rental property is deemed personal interest and therefore nondeductible. (See 10/6/03 issue.) But couldn't that personal portion be treated as "second residence" mortgage interest and therefore be deducted? J.W., via e-mail
A: No. You're allowed to claim mortgage interest deductions for your principal residence and one other home. A residence that you rent out for part of the year may be treated as a second personal residence only if you use it personally more than the greater of 14 days or 10 percent of the time it's rented out. So if you're required to treat your vacation home as a rental property, you won't meet the personal-use test and, therefore, the vacation home can't qualify as a second residence. That means the mortgage interest for periods of personal use is nondeductible.