The mortgage interest deduction is a key tax provision that allows millions of homeowners to offset the mortgage interest paid each year against taxable income. It is among the largest incentives encouraging homeownership in the United States. For taxpayers who itemize rather than using the standard deduction, the mortgage interest deduction is among the most popular — approximately 33 million Americans claimed it in 2016.

Under the new tax plan, which takes effect for the 2018 tax year, on new mortgages you may deduct the interest you pay on mortgage debt up to $750,000 on your primary home and a second home ($375,000 if married filing separately). That's down from the previous limit of $1 million ($500,000 if married filing separately).

Use NerdWallet's mortgage interest deduction calculator to find out what this means for your next mortgage.