According to the IRS...
PRINCIPAL RESIDENCE.
In the case of a taxpayer using more than one property as a residence, whether property is used by the taxpayer as the taxpayer’s principal residence depends upon all the facts and circumstances.
If a taxpayer alternates between 2 properties, using each as a residence for successive periods of time, the property that the taxpayer uses a majority of the time during the year ordinarily will be considered the taxpayer’s principal residence.
In addition to the taxpayer’s use of the property, relevant factors in determining a taxpayer’s principal residence, include, but are not limited to:
(i) The taxpayer’s place of employment;
(ii) The principal place of abode of the taxpayer’s family members;
(iii) The address listed on the taxpayer’s federal and state tax returns, driver’s license, automobile registration, and voter registration card;
(iv) The taxpayer’s mailing address for bills and correspondence;
(v) The location of the taxpayer’s banks; and
(vi) The location of religious organizations and recreational clubs with which the taxpayer is affiliated.
