The 1099 vs W-2 tax difference, in one paragraph
As a W-2 employee, your employer pays half of your Social Security and Medicare (7.65%) and you pay the other half. As a 1099 contractor, you pay both halves — that\'s the 15.3% self-employment tax, on top of regular federal and California income tax. The good news: half of that SE tax is deductible above the line, and most independent contractors qualify for the 20% Qualified Business Income (QBI) deduction, which softens the blow significantly.
How California 1099 tax math works
- Subtract business expenses from gross 1099 income → net self-employment income.
- Multiply net by 92.35% → SE tax base.
- Apply 12.4% Social Security (up to wage base) + 2.9% Medicare → SE tax.
- Half of SE tax is deductible from federal AGI.
- Apply standard deduction and (if eligible) the 20% QBI deduction.
- Apply federal brackets (10–37%) → federal income tax.
- For California: subtract CA standard deduction (no QBI here — California does not conform), apply CA brackets (1–12.3%) → state income tax.
- Total tax = SE tax + federal income tax + CA income tax.
Quarterly estimated payments
The IRS and California Franchise Tax Board both require quarterly estimated payments if you expect to owe more than ~$1,000 federal or ~$500 California at tax time. Underpaying triggers an underpayment penalty even if you eventually pay in full.
Federal due dates: April 15, June 15, September 15, January 15 (of the next year). California due dates are the same calendar dates but use a front-loaded schedule — 30% / 40% / 0% / 30% — meaning your June 15 California payment is larger than your April 15 payment. Most planning software accounts for this automatically.
Which expenses can California 1099 contractors deduct?
California largely conforms with federal rules on Schedule C deductions. Common ones:
- Home office (regular and exclusive use)
- Business mileage (federal rate; California separately allows actual expenses)
- Equipment, software, subscriptions, professional services
- Health-insurance premiums (above-the-line federal deduction; CA conforms)
- Solo 401(k), SEP-IRA contributions (large potential deductions)
- Continuing education, professional licensing
- Business meals (50% deductible)
California does not conform with the federal QBI deduction — the 20% QBI reduces your federal tax but not your California tax. The calculator above accounts for this difference.
Solo 401(k) and SEP-IRA: the highest-leverage 1099 tax savings
A Solo 401(k) lets you contribute as both employee (~$23,500 in 2025) and employer (~25% of net SE income). That can shelter $50,000+ of income, returning 30–45% in immediate combined federal + California tax savings depending on income tier. For most 1099 contractors earning over $80k, opening a Solo 401(k) is the single most impactful tax move.