A little year-end attention to your mortgage could lower your upcoming Internal Revenue Service bill.

Unlike rent, which you pay beforehand (i.e., your Jan. 1 bill covers your stay in the rental unit for that coming month), your mortgage payments are made at the end of your occupancy period. That means your Jan. 1 mortgage statement represents interest for the month of December, making it a tax-break-eligible bill for this year.

By accelerating that payment even by just a day (Dec. 31, if your financial institution is open for business then), you get an additional deduction for the interest paid.

Don't get greedy, though. You can't make your February, or any other upcoming mortgage payment, early to boost your year-end deduction amounts. Tax law generally prohibits write-offs for prepaid interest (there is an exception for loan points in some cases). Each year, you can deduct only that home mortgage interest for that year.

You also want to make sure you don't cut it too close in making the early payment. Get the check in the mail in plenty of time for it to arrive at your lender by year's end. If you pay online, be sure you make the electronic transaction in time to have it credited to your 2007 payment amount.

That way the added interest will show up on the annual statement (usually a Form 1098 or an IRS-acceptable substitute) you'll get from your lender in late January, detailing your deductible mortgage activity.

Timing your payment
Some tax professionals say you can simply make your extra mortgage payment late this month with a check dated Dec. 31 and count it toward your deductions.

However, if you actually get your payment to the bank by the last business day of the year, which happens to be Monday, the 31st this year, or a weekday or two early, the extra interest will show up on the lender's official paperwork. And that means no curious tax examiner will question any difference between the amount you claim on your Schedule A and what your lender reported (and copied to the IRS) on the 1098 form.

-- Updated: Dece. 13, 2007