“$200k cost basis and move it over to a $3 million home. “
That is for income tax calcs. Only $500k per couple is exempt’
If you sell your $200k home for $1 million, you will immediately owe taxes on $300k.
That’s capital gains. I’m talking about transferring your cost basis from your old home to a new residence. It is possible here in CA but again I am not familiar with the particular fine print terms and conditions.
I also know people who went severely underwater in 2009-2010. They asked for a re-assessment. They got it, with the caveat that their home is subject to reassessment every 2 years. Again, not familiar with those particulars either.