The same $8,750 family HSA contribution is two different accounts depending on which return it lands on.

On the federal return

Triple exempt

  • The contribution is deducted from income.
  • Dividends and gains inside are not taxed.
  • Withdrawals for medical costs are not taxed. After 65, other withdrawals are taxed like an IRA.

On the California return

A taxable brokerage account

  • The contribution is added back to state income.
  • Dividends and realized gains inside are taxed every year at ordinary state rates.
  • The account needs its own state tax entries, which most HSA custodians do not prepare.

What it costs

At California’s 11.3% bracket, an HSA holding an index fund with a 1.3% yield pays about 15 basis points a year of state tax on the dividend, plus state tax on any gain the fund realizes or the holder takes. The federal saving on the contribution, 37% of $8,750 or about $3,200 a year, is far larger, so the account still comes out ahead. It is simply not the triple-exempt shelter it is in the other 48 states that conform.

The bill

A California bill to adopt the federal treatment for 2026 through 2030 was analyzed by the state tax agency in 2025 and had not been enacted as of September 2026. Until it is, the location rule for a Californian’s HSA is the taxable-account rule: patient, low-dividend holdings fit best, and anything that realizes gains inside creates a state bill each year.