How do I calculate mortgage interest adjustment for california??

[KurtL1]

The Federal law limited the mortgage interest deduction acquisition debt maximum from $1,000,000 ($500,000 for married filing separately) to $750,000 ($375,000 for married filing separately). California does not conform to the Federal law.

If your mortgage acquisition debt exceeds $1,000,000 ($500,000 for married filing separately) to $750,000 ($375,000 for married filing separately). your mortgage interest was reduced on your Federal return. 

You would calculate the adjustment subtract the mortgage interests reported on the Schedule A from the mortgage interest reported on the Form 1098 from the mortgage lender.

[cherry532]

What does "exceeds $1,000,000 ($500,000 for married filing separately) to $750,000" mean? Could you elaborate more? 

What's the difference when the loan exceeds 1000000 vs when the loan exceeds 750000 but under 1000000?

[VictoriaD75]

The limit on the amount of interest has changed under the Tax Cuts & Jobs Act. The interest deduction pre-TCJA has been available to qualified mortgage debt up to $1 million ($500,000 married filing separately).

Through 2025, the TCJA has lowered the amount of qualified mortgage debt to $750,000. For qualified mortgage debt incurred on or before December 15, 2017, the $1 million limit remains in place, thus "grandfathering" existing mortgage debt.

[Eric D]

How do I calculate this with the following information?

House A purchased in 2015 with an initial mortgage balance of ~$500,000

House B purchased in 2019 with a mortgage balance of ~$1,000,000.  House A turned into rental property 1/2 way through the year.

Is all of the mortgage interest from House A deductible and then the first $750,000 of House B (since purchased 2018 or later)?

Or is all of the mortgage interest from House A deductible and then the first $250,000 from House B?