There are two methods for allocating mortgage interest and property taxes which, actually, TurboTax provides in the program's guidance.
The Tax Court Method vs The IRS Method
The Tax Court allows a different allocation formula for interest and taxes than the one the IRS describes in Publication 527. Under the Tax Court formula, interest and taxes are allocated on a daily basis, that is, the rental portion is the ratio of days rented to the number of days in the year. Under the IRS formula, interest and taxes are allocated in the ratio of days rented to days used. The Tax Court ratio results in a smaller amount of interest and taxes allocated to the rental property.
