If you sold your principal residence during the year and acquired a new principal residence, the deduction for any interest on your acquisition indebtedness (i.e., mortgage) could be limited. The TCJA limits the interest deduction on mortgages of more than $750,000 obtained after December 14, 2017. The deduction is limited to the portion of the interest allocable to $750,000 ($375,000 in the case of married taxpayers filing separately). For mortgages acquired before December 15, 2017, the limitation is the same as it was under prior law: $1,000,000 ($500,000 in the case of married taxpayers filing separately). However, as discussed below, if you operate a business from your home, an allocable portion of your mortgage interest is not subject to these limitations.
You can potentially deduct interest paid on home equity indebtedness, but only if you used the debt to buy, build, or substantially improve your home. Thus, for example, interest on a home equity loan used to build an addition to your existing home is typically deductible, while interest on the same loan used to pay personal living expenses, such as credit card debts, is not.