Personal Finance & Estate › Income, gift, estate & real-estate taxes
Income tax (federal & California)
Since 1913· Tax rule
Law or rule (2026)Set by statute, regulation or the agency; numbers change yearly.
The yearly tax on income, federal since 1913 and California since 1935, charged at rising rates on each slice.
See it on the Personal Finance & Estate map →How it works
Start with gross income: wages, rents, interest, K-1 shares, retirement withdrawals. Subtract adjustments to get AGI, then the standard or itemized deduction and, for business owners, the QBI deduction to reach taxable income. Federal brackets run 10% to 37%; long-term gains and qualified dividends get lower rates. California's rates run 1% to 13.3% on nearly everything. Tax is paid through withholding and quarterly estimates; returns are due April 15, and extensions give six more months to file, not to pay.
Why it matters for you
It is the biggest recurring tax for most people; nearly every account, deduction and real-estate rule on this map works by changing what lands in taxable income.
Rules, limits and sources (2026)
The 16th Amendment (ratified February 1913) allowed it; the 2025 law made the 2017 brackets permanent; the IRS and FTB publish yearly rates and forms.
Watch out for
Economists still debate how much tax rates change work, saving and investment, and Congress revisits brackets often.
Inside this (9)
- One Big Beautiful Bill Act (2025 tax law)
- Federal tax brackets (10%–37%)
- Capital gains tax (short- vs. long-term)
- California income tax (top rate 13.3%)
- Standard vs. itemized deductions (incl. mortgage interest)
- SALT deduction cap (raised to $40,000 in 2025)
- QBI deduction (20% pass-through, Sec. 199A)
- Quarterly estimated taxes & safe harbors
- LLC & partnership taxation (Schedule K-1)
Connections (11)
▸Federal tax brackets (10%–37%) set the rates of Income tax (federal & California)Law or rule (2026)
How they connect
The brackets are the rate schedule of the federal income tax: after deductions, taxable income is sliced into seven bands taxed at 10% to 37%. California runs its own separate ladder, 1% to 13.3%, so a top earner's combined marginal rate can exceed 50%.
When it applies
Congress set the first brackets, 1% to 7%, in 1913; today's seven rates come from the 2017 TCJA and were made permanent in July 2025.
The rule
IRC Sec. 1(j); IRS Rev. Proc. 2025-32 lists the 2026 bands; California's rates are in Revenue and Taxation Code sec. 17041.
Watch out for
Economists debate how much bracket changes affect work and saving; whether future Congresses keep today's rates is open.
▸Capital gains tax (short- vs. long-term) is a part of Income tax (federal & California)Law or rule (2026)
How they connect
Capital gains aren't a separate tax: they are part of taxable income on the same Form 1040, stacked on top of ordinary income. Long-term gains and qualified dividends then get the lower 0/15/20% rates, while short-term gains are taxed as ordinary income. Gains also raise AGI, which can trigger NIIT, IRMAA and phase-outs.
When it applies
Gains were taxed as ordinary income from 1913; the Revenue Act of 1921 introduced a separate lower rate for long-held assets.
The rule
IRC Sec. 1(h) computes the special rates inside the income tax; Form 1040's Schedule D and capital-gain tax worksheet show the mechanics.
Watch out for
Whether gains should be taxed like wages, indexed for inflation, or taxed at death keeps resurfacing in Congress.
▸California income tax (top rate 13.3%) is the state layer of Income tax (federal & California)Law or rule (2026)
How they connect
California's Form 540 starts from federal AGI, then adjusts on Schedule CA: it adds back items California doesn't recognize, like HSA deductions and bonus depreciation, and subtracts others, like Social Security benefits. Then its own brackets apply. State tax paid is federally deductible only within the SALT cap.
When it applies
California enacted its income tax in 1935, during the Depression, and has conformed to federal law selectively ever since.
The rule
FTB Schedule CA (540) instructions list each difference; California's Revenue and Taxation Code adopts the federal code only as of a fixed date.
Watch out for
Whether California adopts parts of the 2025 federal law, such as 100% bonus depreciation, is up to the legislature; historically it rarely follows.
▸Standard vs. itemized deductions (incl. mortgage interest) shrink the base of Income tax (federal & California)Law or rule (2026)
How they connect
Deductions are subtracted from AGI to reach taxable income, the amount the brackets apply to. Every filer either takes the standard deduction or itemizes, whichever is larger. In the 24% bracket, $10,000 more of deductions saves $2,400 federally, but only if itemizing beats the $32,200 joint standard amount.
When it applies
The standard deduction began in 1944; the 2017 law nearly doubled it, and the 2025 law made that permanent.
The rule
IRC Secs. 63 and 67; Form 1040 and Schedule A show the choice; IRS data show itemizers fell from about 30% to roughly 10% after 2018.
Watch out for
Whether the SALT cap drops back to $10,000 in 2030 as scheduled, and how that shifts itemizing, is unsettled.
▸SALT deduction cap (raised to $40,000 in 2025) limits a key deduction in Income tax (federal & California)Law or rule (2026)
How they connect
Before 2018, itemizers could deduct all state and local income and property taxes. The SALT cap limits that deduction on the federal return, raising federal tax for many in high-tax states like California, where state income tax alone often exceeded the original $10,000 cap.
When it applies
Created by the 2017 TCJA at $10,000 for 2018–2025; raised to $40,000 by the 2025 law, with a return to $10,000 scheduled for 2030.
The rule
IRC Sec. 164(b); IRS Statistics of Income data show itemized SALT deductions dropped sharply after 2018.
Watch out for
How much federal relief state taxes deserve is a political fight between high- and low-tax states; the 2030 snapback may be revisited.
▸QBI deduction (20% pass-through, Sec. 199A) cuts federal tax on pass-through income in Income tax (federal & California)Law or rule (2026)
How they connect
The QBI deduction reduces federal taxable income by up to 20% of pass-through business profit, so a top-bracket owner pays about 29.6% instead of 37% on it. It does not reduce adjusted gross income, and California, which does not conform, taxes the full amount.
When it applies
Enacted in the 2017 TCJA for 2018–2025 as a counterpart to the corporate rate cut to 21%; made permanent in July 2025.
The rule
IRC Sec. 199A; claimed on Form 8995 or 8995-A; Treasury's 2019 final regulations define qualifying income.
Watch out for
Economists debate whether it boosts investment or mainly benefits high earners; its complexity invites disputes over what counts as a business.
▸Quarterly estimated taxes & safe harbors prepay Income tax (federal & California)Law or rule (2026)
How they connect
Income tax is pay-as-you-go: wages are withheld, but rents, K-1 income, interest and gains usually aren't. Quarterly estimates fill that gap so the year's tax is mostly paid by January. Meeting a safe harbor prevents underpayment penalties even if a large balance is still due in April.
When it applies
Pay-as-you-go began with the Current Tax Payment Act of 1943, as wartime income tax spread to most workers.
The rule
IRC Sec. 6654 imposes the underpayment penalty; IRS Form 1040-ES and Publication 505 explain the safe harbors.
Watch out for
Whether to pay exactly the safe harbor or closer to actual tax depends on cash needs and interest rates; it's a judgment call.
▸LLC & partnership taxation (Schedule K-1) passes business income into Income tax (federal & California)Law or rule (2026)
How they connect
A partnership or multi-member LLC pays no federal income tax; instead each owner's K-1 share of rents, interest, gains and business income flows onto the personal return, mainly Schedule E. Each item keeps its character: rental income stays passive, gains stay capital, and qualifying business income may get the 20% QBI deduction.
When it applies
Partnership pass-through taxation dates to the 1913 income tax; the 1954 code's Subchapter K set today's rules.
The rule
IRC Secs. 701-704 tax partners, not partnerships; Schedule K-1 (Form 1065) and Schedule E carry the amounts.
Watch out for
Allocations of income among partners, and whether they have 'substantial economic effect', are a frequent source of audits and disputes.
▸401(k) plan defers Income tax (federal & California)Law or rule (2026)
How they connect
Traditional 401(k) contributions, up to $24,500 in 2026, come out of pay before federal and California income tax, and growth is untaxed until withdrawal. Withdrawals are then taxed as ordinary income at whatever rate applies in retirement. Roth 401(k) dollars flip this: taxed now, tax-free later.
When it applies
Section 401(k) was added by the Revenue Act of 1978; IRS rules in 1981 let employers offer salary deferrals.
The rule
IRC Secs. 401(k) and 402(g); W-2 Box 12 code D shows deferrals excluded from taxable wages.
Watch out for
Whether deferring pays off depends on future tax rates, which nobody knows; that is the core of the traditional-versus-Roth debate.
▸Life insurance pays death benefits free of Income tax (federal & California)Law or rule (2026)
How they connect
Death benefits paid to beneficiaries are generally free of federal and California income tax. Cash value grows tax-deferred, and policy loans aren't taxed while the policy stays in force. Exceptions: interest on delayed payouts, policies sold or transferred for value, and employer-owned policies lacking proper notice and consent.
When it applies
The original 1913 income tax already excluded life insurance paid at death; today's rule is Sec. 101(a) of the 1954 code.
The rule
IRC Secs. 101 and 7702; IRS Publication 525 lists life insurance death proceeds as nontaxable.
Watch out for
Income-tax-free isn't estate-tax-free: proceeds count in an insured owner's estate, hence ILITs. How far cash-value policies should serve as tax shelters is debated.
▸Income tax (federal & California) is administered federally by Internal Revenue Service (IRS)Law or rule (2026)
How they connect
The IRS turns the Internal Revenue Code into forms, rules and collection: it processes Form 1040 and its schedules, matches W-2s, 1099s and K-1s, issues refunds and pursues balances. Congress sets rates and deductions; Treasury and the IRS write regulations and guidance. California's share of the bill goes to the Franchise Tax Board instead.
When it applies
The 16th Amendment (1913) authorized the modern income tax; the IRS's predecessor, the Bureau of Internal Revenue, administered it from the start.
The rule
Title 26 of the U.S. Code and Treasury regulations set the rules; the IRS Data Book shows about 160 million individual returns filed yearly.
Watch out for
How far IRS guidance can go is shifting: the Supreme Court's 2024 Loper Bright ruling ended automatic deference to agency interpretations, inviting more challenges.