Can we claim the interest on borrowed money against our home to buy a house to flip in 2018 but we have not sold the flip house yet?

[Gilbert]

Our primary home is paid off, we borrowed money against it.

[Vanessa]

No, you cannot claim it as mortgage interest as an itemized deduction.  However, you would be able to add it to the carrying costs of the investment property.

"If your home mortgage interest deduction is limited under the rules explained in Part II , but all or part of the mortgage proceeds were used for business, investment, or other deductible activities, see Table 2 near the end of this publication. It shows where to deduct the part of your excess interest that is for those activities. The Table 1 Instructions for line 16 in Part II explain how to divide the excess interest among the activities for which the mortgage proceeds were used."https://www.irs.gov/publications/p936#en_US_2018_publink1000229983