The mortgage interest deduction allows homeowners to deduct the interest paid on their mortgage loans from their taxable income, which can result in a reduction in their overall tax liability. However, there are limits and restrictions on the mortgage interest deduction. As of my last knowledge update in 2022, here are the key limits and requirements for the mortgage interest deduction in the United States:

1. Limit on Loan Amount:

   • For loans taken out after December 15, 2017, interest on mortgage debt is deductible for loans up to $750,000 for married couples filing jointly and $375,000 for single filers. This is a decrease from the previous limit of $1 million for joint filers and $500,000 for single filers.

2. Grandfathered Loans:

   • If you took out your mortgage before December 15, 2017, the previous higher limits may apply. This means you may still be able to deduct interest on a mortgage of up to $1 million for joint filers or $500,000 for single filers.

3. Home Equity Loans and Lines of Credit:

   • The Tax Cuts and Jobs Act of 2017 eliminated the deduction for interest paid on home equity loans and lines of credit, unless the funds were used to buy, build, or substantially improve the home that secures the loan. In other words, interest on home equity debt used for purposes like debt consolidation or personal expenses is no longer deductible.

4. Use of Funds:

   • To be eligible for the mortgage interest deduction, the borrowed funds must be used to buy, build, or substantially improve the home that secures the loan. This means that interest on mortgages used for second homes or investment properties may also be deductible, but there are additional limits and restrictions.

5. Itemizing:

   • To claim the mortgage interest deduction, you must itemize your deductions on your federal tax return using Schedule A (Form 1040). If your total itemized deductions are less than the standard deduction, it may not be financially beneficial to itemize.

6. Marriage Status:

   • Married couples must file jointly to take advantage of the higher limit. If you're married but file separately, the limit is reduced to $375,000 for each spouse.

7. Special Situations:

   • In certain situations, such as in the case of a divorce or when a home is transferred between family members, there may be specific rules and limitations related to the mortgage interest deduction.

It's important to note that tax laws can change, and the information provided is based on the rules in effect as of 2022. It's advisable to consult with a tax professional or the most current tax guidelines when preparing your tax returns to ensure you are eligible for and correctly claiming the mortgage interest deduction based on your specific circumstances.