How does turbotax calculate the California interest and points adjustment?

[casio999]

How does turbotax calculate the California interest and points adjustment? The 'California Mortgage and Home Equity Interest' section states, 'We have calculated your California interest and points adjustment based on information provided to us." How does turbotax do this calculation and what information does it use? A number appeared automatically for 'Adjustment for interest and points reported on form 1098' but I cannot find any supporting documentation for how this number was calculated.

I have a home loan with a balance greater than $1M, and it is grandfathered in prior to the 2018 tax law change. Based on this I would not expect a California interest and points adjustment but somehow turbotax calculated there should still be an adjustment.

[KrisD]

To qualify as grandfathered it must have been "secured by your qualified home on October 13, 1987,"

If so, no adjustment would be needed. 

Switch to Forms and look for a home mortgage interest worksheet. 

https://www.irs.gov/publications/p936