Most married couples assume Married Filing Jointly (MFJ) is the obvious choice. Usually it is. But for high-income households in California, the math can sometimes change.
Here's Why California's top bracket is 12.3%. But above $1M of taxable income, the state adds a 1% mental health surcharge—pushing the effective rate to 13.3%.
The problem: that $1M threshold doesn't double for married couples.
Here's an Example A couple with $1.6M in California taxable income filing jointly has $600K over the $1M threshold = $6,000 in extra California tax from the surcharge alone.
Filing Married Filing Separately (MFS) can sidestep the surcharge for the right situation.
If the couple's earnings are roughly even, income splits to ~$800K each. Neither spouse crosses the $1M line. The surcharge disappears entirely.
Same household. Same income. $6,000 saved—just from changing filing status.
This isn't a blanket strategy. Filing separately can backfire if you don't look at the full picture. Federal tax rules are generally less favorable under MFS—certain credits and deductions can be limited or lost, capital gains brackets can shift, and itemized deductions don't always split cleanly.
In California, community property rules can further complicate how income and deductions must be allocated between spouses, which may reduce or eliminate the expected benefit. The result can be higher overall taxes even if the state surcharge goes away.
That's why this must begin as a modeling exercise, not a rule of thumb. The decision only makes sense after comparing both scenarios across federal and state returns together.
Working with a professional tax and advisory team can help you test the options, understand the trade-offs, and determine whether filing separately is actually the smarter move for your situation.
For educational purposes only. Not tax, legal, or investment advice.