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Year-End Mortgage and Tax Planning for California Homeowners: A December Checklist

The end of the calendar year is one of the most overlooked planning windows for California homeowners. With the right moves before December 31, you can maximize your mortgage interest deduction, time a refinance strategically, and minimize your tax exposure. Here’s what California homeowners should be thinking about before year-end. This post is general information only — consult your CPA for personalized tax advice.

Maximize Your Mortgage Interest Deduction

Mortgage interest is one of the largest available itemized deductions for California homeowners. Federal law allows deduction of interest on up to $750,000 of mortgage debt ($1,000,000 for loans originated before December 16, 2017). California did not adopt the federal $750K cap, so California state returns may allow deduction on larger loan balances. If you’re close to the itemized vs. standard deduction threshold, consider whether making your January mortgage payment in December could push you over the line this tax year. The IRS allows deduction of prepaid interest for the month it covers — so January interest paid in December is deductible in the current tax year. Consult your CPA before doing this, but it’s a legitimate and commonly used strategy.

Year-End Refinance Timing

If you’ve been considering a refinance, year-end timing has real implications. Points paid on a refinance are generally not fully deductible in year one — they must be amortized over the life of the loan. However, a December refinance closing generates new mortgage interest that stacks with your existing year’s payments for deduction purposes. On a California jumbo loan, a December refinance may generate meaningful deductible costs depending on the loan structure. Consult your CPA on how closing costs and points are treated in your specific situation before timing a refinance around tax considerations.

Property Tax Prepayment (Post-TCJA)

The 2017 Tax Cuts and Jobs Act capped the SALT (state and local taxes) deduction at $10,000 for federal returns. For many California homeowners — particularly in high-property-tax counties like Marin — you may already be capped regardless of timing. However, if you’re under the $10,000 SALT cap, prepaying your second installment of property taxes in December (if your county allows it) can pull the deduction forward into the current year. Marin County typically allows prepayment — call the Tax Collector’s office to confirm procedures and whether prepayment will be accepted and credited in the current tax year.

The Mortgage Interest Deduction After TCJA: What Changed

The 2017 TCJA nearly doubled the standard deduction, which means many homeowners who previously itemized now take the standard deduction, making their mortgage interest effectively non-deductible at the federal level. If your total itemized deductions don’t exceed the standard deduction, you receive no additional tax benefit from homeownership at the federal level. California did not adopt the $750K mortgage debt cap, so state returns still allow full deduction on larger California loan balances. This creates a split situation: full state deductibility, but potentially zero federal deductibility for some California homeowners. Understanding your specific tax position requires a CPA conversation — not assumptions based on how the deduction worked five years ago.

Home Equity and Cash-Out Planning

If you’re considering a cash-out refinance or HELOC for major home improvements, year-end planning matters. Interest on home equity debt is only deductible if the funds are used to buy, build, or substantially improve the home securing the loan. A year-end cash-out funding a kitchen remodel starting in Q1 positions your next year’s interest as potentially deductible. Keep receipts and document the use of funds — the IRS requires tracing for mixed-use home equity debt. If you use cash-out proceeds for purposes unrelated to home improvement, that portion of home equity interest is not deductible on federal returns. Consult your CPA to confirm the treatment for your specific situation.