You bought your Morgan Hill house in 1998 for $375,000. You're selling in 2026 for $1,850,000. Before you do the happy dance about your $1.47 million gain, sit down. If you're married filing jointly, you'll owe roughly $97,000 in federal and California capital gains tax the April after closing. If you're single, closer to $132,000. Most sellers don't see this coming.

This is the thing every long-time South Valley homeowner needs to understand before they list. If you want the 60-second version for your situation, use our Net Proceeds Calculator. Here's the longer explainer.

When you sell a home, the IRS calculates your "realized gain" like this: sale price, minus selling expenses (commission, transfer tax, escrow, title, NHD, warranty), minus adjusted cost basis (original purchase price plus major improvements with receipts), equals realized gain.

On our Morgan Hill example: sale price $1,850,000, minus selling expenses around $130,000 (~7%), minus adjusted cost basis of $445,000 (1998 purchase $375K + kitchen remodel $45K + roof and HVAC $25K) = realized gain of $1,275,000.

Now you subtract the Section 121 exclusion. If you owned AND lived in the home for 2 of the last 5 years as your primary residence:

Everything above that is taxable. So $1,275,000 realized gain minus the $500,000 MFJ exclusion = $775,000 taxable gain.

Then apply the tax rates:

Federal tax (15%) on $775K = $116,250. California tax (9.3%) = $72,075. Total capital gains tax: $188,325.

In this scenario, married filing jointly: about $188K owed. If you were single, your exclusion drops to $250K and your taxable gain becomes $1,025,000, pushing tax to about $241K. The difference is roughly $53,000 based purely on marital filing status.

The number that surprises most Morgan Hill and Gilroy sellers isn't the commission (5% commission is known). It's that the $500K exclusion feels enormous when you buy and feels small when you sell. In 1998 a $500K exclusion covered basically any Morgan Hill home appreciation scenario. In 2026 it covers about a third of the appreciation on a $1.85M sale.

Three specific scenarios where the trap is worst:

Section 121 cuts in half when you're single ($250K instead of $500K). For widowed sellers, there's a special rule: you can still use the full $500K exclusion if you sell within 2 years of your spouse's death. Past that window, it's $250K.

If you're planning a sale after a spouse's passing and you've got a huge gain, the 2-year window is critical. Don't miss it.

If you converted your primary residence to a rental to wait out the market, the Section 121 clock keeps running but the math gets complicated. You lose the exclusion entirely if you don't live in the home as your primary residence for 2 of the 5 years before sale. Plus you owe "depreciation recapture" on the years you claimed depreciation as a rental, taxed at 25% flat.

This rule bites long-time owners who moved out, rented for 3+ years, and then decided to sell. Their exclusion disappeared while they weren't looking.

No Section 121 exclusion at all. The entire gain is taxable.

For investment property only, there's a 1031 exchange option: reinvest proceeds into another like-kind investment property within 180 days and you defer the capital gains. Not eliminate, defer. The tax basis transfers to the new property.

California and Santa Clara County add a few specifics on top of the federal rules:

Keep receipts for everything on this list. They raise your cost basis and reduce your taxable gain dollar-for-dollar:

What does NOT count (routine maintenance and repairs):

This is the single most valuable habit for long-time homeowners: keep a folder of improvement receipts. A $150K kitchen remodel with receipts saves you roughly $39,750 in combined federal + CA capital gains tax when you sell.

If your expected taxable gain is above $300K, it's worth talking to a CPA before you list. Common moves:

California taxes capital gains as ordinary income. If you're retiring in a year, selling the year you retire (or after) can drop you from the 9.3% bracket to 6% or 8%. On $500K of taxable gain, the difference is $5,000-$15,000.

Structure the sale as a series of payments instead of a lump sum. You recognize the gain over the years you receive payments, spreading the tax bill. Useful if you'd otherwise land in the top tax bracket in a single year.

Reinvest gains into a QOZ fund. Defers and potentially reduces the capital gains tax. Complex, not appropriate for most homeowners, but worth asking your CPA about if the gain is seven figures.

Plug in your numbers at the calculator and you'll get the full closing cost breakdown (commission, transfer tax, escrow, misc), adjusted basis with your improvements, realized gain, Section 121 exclusion applied, taxable gain, federal + CA cap gains tax, mortgage payoff, and net to you.

If the taxable gain is above $100K and you selected "actively listing" as timeline, we offer a free 45-minute pre-list tax + pricing call with a local CPA + agent team. They'll walk you through 1031, installment sale, timing, and comp-backed list pricing in one call before you commit.

Sheena and Ryan cover Morgan Hill, Gilroy, and San Martin in a free weekly newsletter. Subscribe here.