谢谢。 你说的第二点和第三点我能理解。关键是第一点 - 重贷出来的钱， 如果全部拿去投资了另一个投资房。。。

（sorry for not typing chinese...I type too slow)

Let's say I use all of the prceeds from the Cash-out refi loan to buy an investment property, fully paid using the proceeds.

Pub 936's definition of Qualified Home doesn't list pure rental property. And In Part II, it states:

Home Acquisition Debt

Home acquisition debt is a mortgage you took out after October 13, 1987, to buy, build, or substantially improve a qualified home (your main or second home). It must also be secured by that home.

https://www.irs.gov/publications/p936#en_US_2022_publink1000229900

I interpret that "your main or second home" doesn't include your investment home, otherwise it would have list the investment home in the qualifed home list).

I also interpret as the Cash-out refi loan I take on my primary home to buy a separate rental home is still secured by my primary home, not the rental home. Thus leads to my suspision that none of loan interest can be deducted when I calculate my primary mortgage interest deduction on my 1040 Schedule A because the proceed of this refi loan is entirely used to buy and improve my primary home.

Did I miss read something important? Thanks a lot, all.